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rotorque
11th Mar 2001, 16:39
Why does the B206 'Boomerang' (transmission) mounts allow lateral movement but not fwd / aft movement ?

And just for a laugh, if the mast rocks lateraly in flight will the effect be felt as a pitching moment?



Lu Zuckerman
11th Mar 2001, 18:14
To: Rotorque

Is the term "Boomerang" an OZ nickname for a Nodamatic suspension?

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The Cat

[This message has been edited by Lu Zuckerman (edited 11 March 2001).]

rotorque
12th Mar 2001, 06:28
Yep, did ya like it ?

Lu Zuckerman
12th Mar 2001, 06:54
To: Rotorque

Hopefully I don’t come off as an idiot in what I am about to say, as you probably already know.

The Nodamatic suspension is designed to eliminate the two per rev vertical beat that is common to Bell single rotor helicopters. When the Bell blades are aligned with the longitudinal centerline they lose lift and as such the fuselage drops. The Nodamatic allows the transmission to move in relation to the fuselage and the suspension system has calibrated weights that respond to the vertical bouncing of the transmission in relation to the fuselage. The moving of the weights causes a counter force to resist the movement and it cancels out the vertical beat in the fuselage. The way the Nodamatic is hinged I would assume it would allow lateral movement of the transmission when not in operation but not fore and aft. The primary movement is up and down during flight but I would think that if the trannie can be displaced laterally when static that some lateral movement could take place when maneuvering. I think.

Bell uses a similar concept with the bob weights on the 412 rotorhead. These weights are used to cancel out the traveling wave on the blades. Similar weights are used on BK helicopters and Sikorsky uses a system called BI Filar on the rotorhead.


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The Cat

[This message has been edited by Lu Zuckerman (edited 12 March 2001).]

rotorque
12th Mar 2001, 10:06
G'day Lu,

Thanks for that. The bell 206L uses the nodal type system that you described, although it looks complicated when you first open the cowls, it's not that hard to follow the reasons behind the engineering. Your description is pretty good.

I probably answered your question a bit too quick. The boomerang mounts that I was really talking about are the ones on the smaller basic 206. They don't have the 'nodal' system as such. There is literally two mounts that run longtitudinaly supporting the transmission and therefore mast, head etc. They are shaped as a 'boomerang' or a triangle I guess, with the apex attached to the MRGB and the two bases of each triangle attached to the roof of the cabin. The MRGB attachment bearing and lower attachment bearings allow movement from side to side, but not for and aft. The actual movement of the MRG is a form of 'paralelogram' in as far as the MRG will not tilt - just shift position lateraly, so the last question that I asked was just for fun (in a way).

But my question on why there is freedom to move lateraly and not longtitudinaly still stands.

Why is it so?

The Sultan
12th Mar 2001, 13:41
The 206B has a focal pylon to minimize 2/rev vibration due to inplane rotor forces. The focal pylon does allow movement both fore-and-aft and laterally. The f/a pivot is at the top of the "boomerang" and the lateral is at the bottom. Since the pylon mount(spring) is a the bottom, it is relatively easy to move the pylon by hand in the lateral direction. It is much harder to move the pylon in pitch due to the moment arm.

The Sultan

rotorque
12th Mar 2001, 20:09
To The Sultan,

You're a good man. Thanks.

Why is it that, as Lu says, the blades lose 'lift' when longtitudinaly aligned?

This is all new to me.

Lu Zuckerman
12th Mar 2001, 22:39
To: Rotorque

Think about blade stall and what causes it. On blade stall there is a large portion of the blade where there is neutral airflow over the retreating blade and from that point inward the airflow is reversed in an increasing manner the closer you get to the center of the rotor disc. In the case of losing lift when the blades are aligned with the longitudinal centerline the airflow is passing down the span of the blade. Although the blade is still lifting it is lifting less when aligned with the centerline of the helicopter. In this case the decreased lift causes the helicopter to drop. As the blades move from that position the lift starts to increase until the blades are aligned with the lateral axis of the helicopter. During the transition from longitudinal alignment to lateral alignment the blade lift increases and the helicopter starts to rise. The Nodamatic suspension isolates the fuselage from the dynamic system and the linkage and bob weights on the Nodamatic system isolate the helicopter from the up and down movement of the dynamic system and absorb the transmitted energy thus providing a very smooth ride.

However the up and down movement of the dynamic system in relation to the fixed engines can result in problems. This was a significant problem on the original 214s and hopefully by now the problem has been solved. On the 214 the relative movement between the gearbox and the engine caused a two per rev misalignment on the short shaft causing the couplings to pump the lubricating grease out of the coupling.

This grease was picked up in the inlet airflow to the engine and the grease plated out on the engine inlet bell. The grease attracted sand and other small FOD and this disrupted the airflow into the engine. The disrupted airflow caused engine surging and in rare occasions it caused compressor stalls. When compressor stalls were noted the entire driveline and dynamic system had to be replaced and the removed elements had to be inspected and in most cases, discarded. It also increased the maintenance on both the engine and the short shaft as the grease had to be replenished and seals replaced and the engine had to be washed to remove the trapped contaminants from the engine inlet bell.


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The Cat

[This message has been edited by Lu Zuckerman (edited 12 March 2001).]

rotorque
13th Mar 2001, 09:44
Thanks Lu,

It all makes sense now. I had a lot of trouble getting around the fact that there is a loss of lift when the blades are aligned for and aft. I assumed that the total lift would remain constant throughout each revolution.

I have stuck this one in my little black book of silly questions. If you're wondering this little book is huge.

Cheers.

Vfrpilotpb
13th Mar 2001, 14:00
Good Morning(it is here in the UK) this is a question for Lu, the lack of lift associated with the two blades on the 206, is that a problem with all two bladers irrespective of manufacturer or just the Bell types.
Peter R-B UK

Lu Zuckerman
13th Mar 2001, 18:54
To: Vfrpilotb

This is off the top of my head but I would think that the Hiller helicopters would be subject to the same phenomena because of similar blade speeds to that of the Bell. However I don’t think the Robinson would be susceptible to the two per rev bounce because of the high rotational speed of the blades but I could be wrong.


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The Cat

The Sultan
14th Mar 2001, 05:39
Lu,

Your wrong!

All two bladers have 2/rev, all 3 bladers have 3/rev, all 4 bladers have 4/rev, etc, etc, etc. Its called N/rev.

Helicopters of all types require vibration attenuation of some sort to combat N/rev. Generally, this type of treatment equals between 1 to 2% of the aircraft's weight regardless of the number of blades to achieve an acceptable "g" level in the occupied spaces.

The Sultan

Lu Zuckerman
14th Mar 2001, 06:23
To: The Sultan

The elements that you alluded to being employed to dampen out what you call N-rev do exactly that but not for the reasons you gave. These systems are dynamic in nature and are installed on the rotor heads of some helicopters to dampen or eliminate the vibrations caused by the blades and their reaction to pitch and load changes. These cyclical loads cause a traveling wave that if not stopped would cause a cyclical load to be applied to the rotorhead and reflected in the airframe and felt by the pilots and crew/passengers.

Sikorsky uses the Bifilar system that has very heavy bob weights that are disposed between the blades. With centrifugal force the apparent weight of the bobweight is significantly increased. The traveling wave in order to get to the rotorhead must displace the weight from its’ radial position. To move the weight causes energy to be absorbed and the wave is cancelled. The MBB-105 and the BK-117, Bell 412 and some Hughes helicopters including the early version of the Apache have bob weights that are connected in most cases to the blades.

Some helicopters have two types of bob weights that are sensitive to different frequencies of the wave. Some Bell helicopters employ a static weight that is embedded in the blade at the nodal point for the wave in order to cancel it out by absorbing the energy of the wave. The Aerospatial helicopters have a heavy weight suspended on top of a stiff spring with the assembly being mounted on top of the rotorhead. Boeing Vertol has a mechanism mounted under the pilots’ seats to perform the same function.

It is my understanding that Bell developed an electromechanical system that worked in the same manner as a noise-canceling headset. The device sensed the vibration level and the cyclical frequency and generated an opposite sine wave and equal in magnitude which eliminated the vibration. This device was going to be installed in B-205s and HU1s but I don’t know if it was ever placed in wide use.

I do not believe that the incorporation of any of these energy absorption systems was incorporated to compensate for the loss of lift on a two blade or, a multi blade helicopter when the blade are disposed over the longitudinal axis of the helicopter. To eliminate the vibration problem Bell came up with the Nodamatic suspension system which isolates the dynamic system and the transmission from the airframe. When they went to a four-blade system on the 412 they incorporated the bob weights. Some Bell four blade heads do not incorporate the bob weights so I would assume that they went back to the embedded weights.

It is my opinion that the N-rev is in effect the reason these systems were developed with the N-rev being caused by the induced vibration resulting from the traveling wave..


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The Cat

[This message has been edited by Lu Zuckerman (edited 14 March 2001).]

chuckolamofola
14th Mar 2001, 10:30
Lu,

Not all of the N per rev. systems are dynamic. On the 206B the isolation mount reduces the lateral 2 per rev generated by the 2 bladed m/r system. The isolation mount is nothing more than a rubber shock absorber.

As the Sultan pointed out 2 bladed rotors have a 2 per rev and 3 bladed 3 per etc. I don't know if the reason is due to the traveling wave or not but this same phenomena can be measured in ground based fan systems. This is also known as the "Blade Passage Frequency"

In addition to the BOB weights as you called them the (Bell calls then Pendulum Absorbers), the 222 employs a Nodel Beam System to reduce the vertical 2 per rev's and a nose Frahm damper to reduce the lateral 2 per rev's. All three are dynamic but only one is mounted on the rotor. Which one reduces the traveling wave?

In addition to the SPA's (Simple Pendulum Absorber) you mentioned on the Bell 412 they also employ a nose Frahm dampner for lateral 4 per rev. reduction. The 412's you saw without SPA's were probably Agusta made as they have some customers that would rather live with the payload gain than having a smoother ride and the associated payload loss when the SPA's are installed. Weights haven't been added to m/r. The 407 doesn't have SPA's but does have the Frahm damper installed on top of the rotorhead.

Sikorsky uses the Bifilar on the 76 to reduce the 3 and 5 per rev's and a mass absorber similiar to the Frahm to reduce cabin 4 per rev's on later models. On the S76A model they use the VTA (Vertical Trim Amp.)to reduce the vertical 4 per rev. This unit mounted in the nose uses a combination of hydraulics and electronics to perform the magic feat.

The Aerospatial (ECF) AS350/355 employ the spring mass on top of the head to reduce lateral 3 per rev's and then hammers under the pilot's seats to reduce the vertical 3 per rev. The hammers are just a weight mass mounted on a flat spring and tuned to reduce the verical N per rev. of the m/r.

I don't know if I agree with your statement regarding loss of lift as the blade passes over the longitudinal axis. If this happens as you say then on a two bladed rotor one would think you would feel a 1 per rev. and on a 4 bladed rotor you would also experience a 1 per rev. In flight a 1 per rev. that is not a result of mass imbalance is usually caused by the unequal lift of one m/r blade.

Based on your theory of the traveling wave, what would cause a 2 per rev. imbalance on a Bell 412?

With respect to your 2 per rev in engine to transmission driveshaft, most any driveshaft that is misaligned will show a 2 per rev of shaft speed. I doubt the 2 per rev caused the grease loss but more likely was caused by burping the grease from the seals due to misalignment.

Chuckolamofola

Lu Zuckerman
14th Mar 2001, 22:13
To: Chuckolamofola

First of all, I would like to congratulate you for knowing the technical names of the dynamic and electrical elements used to decrease or eliminate unwanted vibrations on helicopters. Some of these units were created after I left the respective programs and I have never worked on some of the programs so my information comes from Aviation Leak and Space Technology, Rotor & Wind and other trade journals. My responses are keyed to the numbered paragraphs in your post (Below)

1) Not all of the N per rev. systems are dynamic. On the 206B the isolation mount reduces the lateral 2 per rev generated by the 2 bladed m/r system. The isolation mount is nothing more than a rubber shock absorber.

2) As the Sultan pointed out 2 bladed rotors have a 2 per rev and 3 bladed 3 per etc. I don't know if the reason is due to the traveling wave or not but these same phenomena can be measured in ground based fan systems. This is also known as the "Blade Passage Frequency"

3) In addition to the BOB weights as you called them the (Bell calls then Pendulum Absorbers), the 222 employs a Nodal Beam System to reduce the vertical 2 per rev's and a nose Frahm damper to reduce the lateral 2 per rev's. All three are dynamic but only one is mounted on the rotor. Which one reduces the traveling wave?

4) In addition to the SPAs (Simple Pendulum Absorber) you mentioned on the Bell 412 they also employ a nose Frahm damper for lateral 4 per rev. reduction. The 412's you saw without Spa’s were probably Agusta made as they have some customers that would rather live with the payload gain than having a smoother ride and the associated payload loss when the SPA's are installed. Weights haven't been added to m/r. The 407 doesn't have SPA's but does have the Frahm damper installed on top of the rotorhead.
Sikorsky uses the Bifilar on the 76 to reduce the 3 and 5 per rev's and a mass absorber similar to the Frahm to reduce cabin 4 per revs' on later models. On the S76A model they use the VTA (Vertical Trim Amp.)to reduce the vertical 4 per rev. This unit mounted in the nose uses a combination of hydraulics and electronics to perform the magic feat.
The Aerospatial (ECF) AS350/355 employ the spring mass on top of the head to reduce lateral 3 per rev's and then hammers under the pilot's seats to reduce the vertical 3 per rev. The hammers are just a weight mass mounted on a flat spring and tuned to reduce the vertical N per rev. of the m/r.

5) I don't know if I agree with your statement regarding loss of lift as the blade passes over the longitudinal axis. If this happens as you say then on a two bladed rotor, one would think you would feel a 1 per rev. and on a 4 bladed rotor you would also experience a 1 per rev. In flight a 1 per rev. that is not a result of mass imbalance is usually caused by the unequal lift of one m/r blade.
Based on your theory of the traveling wave, what would cause a 2 per rev. imbalance on a Bell 412?

6) With respect to your 2 per rev in engine to transmission driveshaft, most any driveshaft that is misaligned will show a 2 per rev of shaft speed. I doubt the 2 per rev caused the grease loss but more likely was caused by burping the grease from the seals due to misalignment.

General response:

Sikorsky first discovered the traveling wave phenomenon when they installed a movie camera on top of an S-51 rotorhead that was mounted on a whirl stand. Sikorsky was looking for indications of leading and lagging and they found two things that they had not anticipated. Up until that time it was thought that the advancing blade lagged due to increased airloads and the retreating blade led due to decreased air resistance. The opposite was found to be true. What they also discovered was that the blades as viewed spanwise looked like a sinusoidal wave used in describing AC electrical flow. It is my understanding that when this movie was shown to helicopter pilots some of them stopped flying.

Responses:

1) The N per rev I was addressing on the Bell has to do with the alignment of the blades along the longitudinal axis and the loss of lift. This causes a two-per-rev vertical beat and has nothing to do with a lateral beat. I would think that if you have a lateral beat it relates to an imbalance condition.

2) I agree with what The Sultan stated about the vibrations on helicopter blades in general. As I indicated in (1) above the vibrations can be traced to one of several phenomena. On two bladed rotor system the vertical beat can be traced to the alignment of the blade as on a Bell. The other vibrations can be traced to an imbalance in the rotor system or, the presence of an uncompensated for traveling wave.

3) If the Bell philosophy carried through from other designs none of the described elements counters the traveling wave. As I had indicated in my post, Bell embedded a weight in the blade at the nodal point of the traveling wave and it is this weight that stops the wave from reaching the rotorhead.

4) I had indicated that the 412 rotor system had the pendular weights but that other Bell four blade systems did not. I also alluded to the fact that they may have reverted to the embedded nodal weights in the blades. It was my understanding that the Bifilar system was developed to counter the traveling wave generated vibrations. Whether they were three per rev or five per rev I can’t say. The system you described by Sikorsky that employs hydraulics and electronics was I believe developed by Hughes and was never used by them. The system has sensors that detect the vertical beat and sends a signal to the hydraulic servos to extend or retract to counter the vertical beat by introducing a countering pitch change. On all of the other elements we agree. I just didn’t know the correct names.

5) On a two-blade system you feel a two per rev vertical beat because the blades comes into alignment with the longitudinal centerline twice in a 360-degree rotation. The one per rev you described on a four-blade system could relate to an out of track on one of the blades. Using my theory to explain why you don’t get the vertical beat on a four-blade system due to the alignment of two blades with the centerline of the helicopter is that you still have two blades generating lift. I don’t know if this is true or not but, you don’t get this type of a beat on a four blade system unless something is amiss.

6) As described in my post this grease pumping phenomenon was first discovered on the 214 because of the movement of the transmission relative to the fixed engine. Assuming a rotational speed of 250 RPM on the rotor, the engine to transmission misalignment occurred 500 time per minute. The misalignment could be several inches depending on the maneuvering of the helicopter. This is what I stated in my post and you agreed with it. The two per rev caused the problem and the Nodamatic suspension compensated for it.

Here is an after thought:

The traveling wave has always been present on helicopter blades from the very beginning but the resultant vibrations were determined to be acceptable to pilots and passengers. When the problems began to surface was when helicopter manufacturers began developing and installing high lift blades which unlike previous designs, which were symmetrical, the new high lift blades were unsymmetrical. The symmetrical designs had highly predictable aerodynamic characteristics where the unsymmetrical blades did not. Unsymmetrical blades want to climb and dive and as such must be restrained by fixed points on the rotorhead and in the flight control systems. This locks the forces in the blades and external devices were incorporated to eliminate or at least minimize the resultant fuselage vibration.

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The Cat

[This message has been edited by Lu Zuckerman (edited 14 March 2001).]

Heliport
20th Oct 2001, 10:47
Just found a useful (well I think it is!) website with an on-line manual for the TH-67 (JetRanger).
It's the site of a company which conducts "Initial Entry Rotary Wing Flight Training" for US Army Aviation Center in Fort Rucker, Alabama, and provides the US Army supplement to the FAA approved Flight Manual.
Click here:
B206 Manual (http://www.lsirucker.com/TECH_LIB/Operators%20Manual/operators/TH67_Main.htm)

Does anyone know of any similar sites?

[ 20 October 2001: Message edited by: Heliport ]

Hoverman
22nd Oct 2001, 01:54
Superb site.
Everything you could wish to know about flying and operating the 206.
An amazing reference point.

Steve76
22nd Oct 2001, 07:24
Very very impressive.
Someone had a lot of time and patience on their hands.... :)

Vfrpilotpb
22nd Oct 2001, 12:27
Heliport,
Thank you for pointing it out, spent most of a very wet Sunday with square eyes, what a good site it is!! ;)

paulgibson
2nd Nov 2001, 16:51
Does anyone know the official Bell explanation for the horizontal stabilizer on a Longranger extending out further on one side than the other and for the fins on the end of the stab being offset opposite to the vertical fin orientation. My guess is to help direct airflow onto the vertical fin to increase it's efficiency. I'm sure all the aerodynamicists I read here will have theories as well and whilst I will be interested to hearing them I would like to know the Bell story in particular.

Arm out the window
5th Nov 2001, 09:01
Yes, and while you're at it, Bell experts, would you mind also giving the reason why the 205 sync elevator is rigged asymmetrically, i.e. one side more nose up than the other?

My guess was that it was to counter inflow roll, but that's all it was...a guess!

paulgibson
7th Nov 2001, 03:30
I would have thought someone would have had some idea re my original question, OK maybe just a guess then. Or is this forum only interested in S76's and robbie's?? :)

sprocket
8th Nov 2001, 02:19
Papagolf: From some course notes referring to the stabiliser ‘end plates’ ….
They are attached to the ends of the stabilizer by means of angle brackets and are offset 5 degrees to the left of centreline to provide a 0 degree angle of incidence to the air flow over the tailboom to improve dihedral (roll) stability of the aircraft in forward flight
..... I presume, as you say, that it stabilises the airflow to assist the vertical fin (which has a 5½ deg offset to the right of centreline) in doing its ‘thing’.
I have not seen any mention of why the stabiliser is mounted slightly further to the left side of the boom. But could have something to do with the tailrotor being mounted on the left side or the main rotor wash coming down from that side.
But why doesn’t the 206B have the end plates fitted?

AOTW: What is ‘inflow roll’? I vaguely remember hearing the asymmetric setup of the 205 synch elevator was to assist in stability during autorotation. ( originally thought somebody had stuffed up the installation)
:D

John Eacott
8th Nov 2001, 11:14
According to our Australian Bell rep., who tends to be fairly clued up, the 206L originally had no end plates, but had gihugeous fairings on the aft cross tubes. The requirements had to do with stability for IFR, and was then met by adding the end plates to the horizontal stab and removing the fairings. The angles on the end plates are optimised for cruise conditions, and are predicated on the rotor downwash in cruise.

The 205 differential in incidence angles on the horizontal stab intrigued me, since the reply given was that it is optimised to give stability of airflow and rotor downwash in REARWARD flight!! The 205/UH1 is certificated for 35 knots backwards, hence the differential stab incidence. Cf the 212, which is NOT certified for such speeds backwards, and has equal angles on the stab.

If anyone has a different explanation, I'm only repeating what I got from the Bell rep...... ;)

paulgibson
8th Nov 2001, 12:55
My guess why not on a Jetranger is that it has a shorter tail boom and presumably (I've never measured it) less distance from the downwash which can be utilised by the vertical fin.

Inflow roll is another name for transverse roll which is a fore and aft dissymetry of lift. As the heli move forward the rear part of the disc receives airflow that has a greater induced velocity and therefore decreased angle of attack. The gyro precession that occurs means less lift on the R/H side (US heli) and a subsequent roll to the right. particularly noticeable as you pass thru ETL when you need left cyclic and right pedal to maintain roll and yaw attitude.
Thanks for the replies

Coriolis
14th Nov 2001, 02:14
Papagolf,
From my 206 course (& memory)the explanation of the fins goes:
In the beginning was the 206 which had a vertical fin to provide antitorque in the cruise, offloading the tail rotor in this regime - then came the stretched version (206L) which had a longer distance from mast to tailfin, which overdid the antitorque effect in the cruise. For reasons of ease and retaining parts commonality it was easier to add opposing finlets to the tailplane ends and keep everything else the same!
Nothing official on that of course, but it sort of hangs together in the practical/beancountery sort of world we have...
Hadn't noticed the tailplane ends longer on one side though...

Hope it helps.. :)

tigerpic
9th Dec 2001, 09:34
somebody taught me this some time ago, but my memory do fade. i'm soon starting to fly an longranger 3.

i need a description of how the fuel system works in the 206 concerning the forward fuel cells. what is the reason for the fuel quantity switch in the cockpit for the forward fuel cells? cg?


cheers

sprocket
9th Dec 2001, 12:08
tigerpic:

The longranger fuel system has a fuel cell under each of the rear facing seats, which normally transfer fuel to the rear cell via jet pump. The only boost pumps are in the rear cell and supply the motive force for the jet pump.
The fwd cells should empty into the rear cell before the rear cell runs low.


Extract from UK AIR Accidents site.

Fuel is transferred from each forward cell into the main fuel tank by the action of a dedicated dual element ejector (jet) pump powered, respectively, by fuel under pressure from the output side of the left and right fuel boost pumps sited on the floor of the main tank. These fuel bleeds are passed through wire mesh filters/check valves upstream of the jet pumps and are sensed by flow switches. Loss of the fuel flow is indicated to the pilot by the respective boost pump warning light. Thus if the fuel pumps were to fail, or the supply in the main tank becomes exhausted, then these lights should illuminate. Fuel quantity in the main and additional tanks is measured using capacitive type sensors, their outputs being summed and presented as a total quantity on a single gauge on the instrument panel. As the forward tanks are interconnected, the single probe fitted to the left forward tank normally senses the quantity in both forward tanks.


Scenario:
If the jet pump becomes blocked, fuel will stop transferring to the rear. The fuel can then be used up in the rear cell when there is (apparently) ample fuel according to the qty indicator.
There are warning lights that will indicate if the motive flow is stopped, but have been ignored because there is still a pressure indication. The next indication will be a low fuel light but this can be ignored because the fuel qty indicator is reading the fwd cells quantity, which has stopped supplying the aft cell.
The next indication will be an engine out warning!

Moral of story: Always believe the low fuel light!

The fuel switch at the qty indicator will no doubt be there to assist in confirming if you have a jet pump problem.

The 206L fuel system has caught people out in the past and it is a good idea to understand it fully if you fly or fix them. The flight manual should have the info you need if you fly them.
Check this incident below. There is a diagram of the 206L1 fuel system given.


edited to edit some editing!

[ 09 December 2001: Message edited by: sprocket ]
206L 1 incident (http://www.aaib.dtlr.gov.uk/bulletin/jul01/n206dd.htm)

[ 09 December 2001: Message edited by: sprocket ]

paulgibson
9th Dec 2001, 13:22
The L/R fuel system I agree does require a better understanding than most but given good preventitive maintenance (cleaning of in-line filters regularly) there is no problem with it.

Although in saying that the 407 has done away with ejector (jet) pumps in favour of boost pumps in the forward (1 only) cell.

The L1 didnt have the ability to indicate fwd tanks quantity independantely, an improvement bought in for the L3.

But in either machine dont ignore the 'Fuel Low' light. :)

Steve76
9th Dec 2001, 20:45
Check the RFM.

B Sousa
9th Dec 2001, 21:33
These have been a real thorn in Bells Ass for many years. They just settled a big Lawsuit in California regarding this and the fact the pilot flew it to empty (deep pocket lost, go figure). As stated before the flight manuel covers the Normal operation and Emergency procedures, I think fairly well. Be cautious if you like to see the needle close to empty. As for me, Fuel in the Truck does you no good.

EESDL
13th Dec 2001, 15:47
One area where you could get caught out if you regularly swap between the JR and LR, is the consequence of a fuel pump failure. As I understand it:
Failure in a JR -n problem - 6000' etc
Failure in a LR - lose 10 gals worth of fuel:-(

Devil 49
13th Dec 2001, 17:09
Long Ranger has 3 cells... Blah, blah, blah.
When refuelling, when sufficient added fuel on board, fuel flows by gravity forward. Simple arrangement, a tube of given height in main leads to forward cells. Below that amount, fuel added to main only.

Long Ranger transfers fuel from forward cells by a sort of venturi effect. Boost pumps also produce flow thru transfer lines. BUT you can have working boost pumps (producing pressure) without flow thru transfer lines and jets (forward cell pumps), so fuel might not be transfer back to main. Fuel in forward cells is unusable.

The fuel quantity indicated on the gauge is total of all 3 cells. If no flow thru forward jets, then no transfer, and the fuel in the forward tanks is stranded. Now you have an unreliable fuel quantity indication.

Activating the switch tells you how much fuel in forward cells. Subtract from total, you know how much in main cell and available.

Yes, all this is for CG management. Requires pilot understanding, and some basic math.

paulgibson
14th Dec 2001, 11:38
Devil 49
just a small technical point on your post....

The loss of fuel transfer does not make the fuel quantity indication unreliable, but I know what you were meaning.

Cheers :)

paulgibson
14th Dec 2001, 11:46
not wanting to seem like a smart arse but just read EESDL's post as well and boost pump failure in a L/R is not as clear cut as you state.

you would need a dual boost pump failure to lose all capability to transfer fuel, and dont forget that if you have much less than 280-300lbs on board then you have used all of the usuable fuel in the forward tanks anyway so a dual failure at that stage is of no real problem (notwithstanding sucking air etc.)

B Sousa
14th Dec 2001, 20:19
PapaGolf. I think along the same lines as you regarding this matter. Just the amount of postings show that the confusion is still there and problems can still occur....
If its below the top of the Range Extender, its time to refuel.........Ha Ha

paco
29th Jan 2002, 22:34
Try this one out:

<a href="ftp://www.electrocution.com/pub/users/electroc/206cg.xls" target="_blank">ftp://www.electrocution.com/pub/users/electroc/206cg.xls</a>

This one shows the lat CG and also changes the sg of the fuel according to OAT - it even calculates the fuel's own changing arms, but does not recognise 75 US gals - it was too near to 76 US Gals to make a difference anyway.

cheers

phil

EESDL
31st Jan 2002, 10:16
Thanks for that but unfortunately the links not working on the PC i have to use.....stuck out in the Omani wilderness.. .Bit of research required, if you would,. .noticed hat you are from NS. What do you know of Cougar Helicopters? I was in Halifax the other night (great night..Lower Deck, Rogues Roost, Economical Shoe Company and the Canadian girls, what socialable ladies) I digress, we were trucking further west and night-stopped at Halifax. Cougar seemed fairly busy with Off-shore work, any idea on the size of the company etc?. .PS Trim sheet in the relevant section of <a href="http://www.robertsaviation.flyer.co.uk" target="_blank">www.robertsaviation.flyer.co.uk</a> caters for the Longranger aswell, if that's any use to you.

paco
31st Jan 2002, 14:46
I think if you right click, it might give you the opprtunity to save the file.

I know Cougar very well - I work for them! In the VFR division, though, but from what I see the guys with the wheels seem to be working quite hard.

I must say it's the best helicopter company I've worked for, except those I've run myself <img src="smile.gif" border="0">

There are 35-ish pilots, some Pumas in Newfoundland, a 61 & 76, Twinstar and 2 206s in Halifax.

. .phil

[ 31 January 2002: Message edited by: paco ]

[ 31 January 2002: Message edited by: paco ]</p>

EESDL
1st Feb 2002, 06:34
Thanks

Hone22
23rd Feb 2002, 14:32
Hi all,

Well the ol battery in the 206 has been a wee tad low on the charge thing recently. 1st start today 25c 2000ft amsl, very slow to spool up to 12% - crack fuel modulate flow to keep TOT in hand. Turbine lights off but still slow in building to the 58% start cut out.

After a 1 hr flight, no probs genny or elsewhere, shutdown for about 3hrs. Try a restart, lucky to get 12%, crack fuel, lights off but going nowhere. Look after TOT but no accelaration whatsoever N1, Abort start go home drink wine and post this.

Comments? Any tips out there (apart from the obvious, new batt or grd pwr for starters).

Any Ol hands with the low down on 206 starts (ceco fuel governor) please add your pearls of wisdom re starts and general do's don't you follow with this darlin'

Cheers & fly safe. .Hone

sprocket
23rd Feb 2002, 17:03
Wisdom can be a hard earned thing. Whatever you hear or do ...

1. Dont burn the the hot end off.

2. Get it looked at/fixed before somebody does burn the hot end off.

3. Oh, and did I mention, dont burn the hot end off!

Good Luck!

Steve76
23rd Feb 2002, 17:24
Gidday Hone,. .Check the starter contactors in the nose, they contain a copper bar and we used to get a lot of corrosion on them around rotovegas.. .Sometimes a poor contact will prevent starting altogther. You should also clean and check the terminals on the genny and batt.. .Cher cher bro!. . :)

Devil 49
23rd Feb 2002, 17:42
Gotta have more electrons. The battery is your source of power until the engine has the turns to keep the flame contained. The other demands on the battery, like boost pumps, etc., are minimal compared to getting the NG up to 58.. .When you have the techs attention, consider that starter/generator carefully. If you're using a nicad, you most likely have a simple battery and charging problem. But the starter could be getting weak too.. .Go easy on the introducing fuel at 12 per cent... That's the sorta thing that's great on occasion (emergency) but will cost you money in the long run. 14 or better makes me happy.

tgrendl
23rd Feb 2002, 19:57
Look to see if you're getting coking also. When you shut down try to turn the blades back gently. If they don't want to go freely or are stuck you've probably got a coking problem in the motor.

If so increase cooldown times and immediately after blades stop rotate them backwards 2-3 revolutions.

This will work for a while but eventually you'll need the engine man in.

Good luck

paco
23rd Feb 2002, 23:19
Although Allison have issued a letter stating that it's OK to crack the throttle at 12-13%, it's on the basis that the acceleration through that point is lively. If it's at all slow at that point, please, please don't attempt a start unless there's a polar bear coming! <img src="smile.gif" border="0">

OK Chief Pilot hat off...

Either the battery is not accepting a charge, in which case it might be sulphated (did someone leave it on before?), or it's not getting it, either because the genny is not sending it or there's something stopping it. I would certainly look at those bars (some guys even carry spares) and get the battery checked.

Hope that helps!

phil

Lu Zuckerman
23rd Feb 2002, 23:54
This is from my deepest memory so I may get it cockeyed. If you have a lead acid battery then much of what Paco and the others have said is true along with the possibility of coking. You have a nickel cadmium battery then it requires periodic maintenance, which involves a complete discharge and recharging. A Ni Cad battery will develop a memory and with that memory it will only accept that level of charge and no more. If this is the problem then the battery does not have the ooomph to turn the engine over to light off speed assuming coking is not involved. Turning the main rotor backwards will give an indication of coking, as it will impede your ability to rotate the blades. If the coking level is low then the rotation of the blades backwards will break the engine rotor free. In either case, check the engine and check the battery log book to determine when the last maintenance was performed assuming a Ni Cad battery.

Hone22
24th Feb 2002, 03:59
Hi all,

Thanks for all the pearls, it's zackly what this forums about. Keep it up!!!

Battery's a Ni-Cad, deep cycled bout a mth ago.

What i learned from the postings.

1.Don't burn the hot end off.

2.Best min 14% before fuel intro, so as not to burn the hot end off.

3.Full batt ommphh, will help avoid burning the hot end off.

4.Check all terminals, said copper bar re-batt oommphh as per # 3.

5.As Batt deep cycled (& supposedly ok) probably a genny issue.

6. Coking could be a prob, but o'haul recently so maybe #5.

7. Don't burn the hot end off.

Thanks all. .Cheers & fly safe. .Hone.

Ps: Steve76 Kids from +40c to -40c, thank god they're so adaptable, ay! <img src="tongue.gif" border="0">

tgrendl
24th Feb 2002, 09:50
Hone 22

Overhauled recently scares me with that problem coming up.

Be carefull

Steve76
24th Feb 2002, 11:03
Right On Lu. Memory is a big prob. Well thought of.. .Hone - send me mail mate.. .Cher de cher kapai bro :)

Hone22
24th Feb 2002, 11:05
tgrendl said

Hone 22. .Overhauled recently scares me with that problem coming up.

Be carefull

Please elaborate, I'm all ears (eyes? ya get me)

cheers & flysafe. .Hone

sprocket
24th Feb 2002, 12:56
Hone22:

The coking problem mentioned above, as far as I’m aware only affects the N2 turbine labyrinth seal and will not cause the starting problems you originally mentioned. I have seen the N1 get up to 30% during start without the blades turning [due to a coked turbine] before the start was aborted. Up until then, the start sequence looked normal. [A bit like leaving your tie-down on]

I have not seen a 206 with a nicad for many years, unless the helicopter was new from the factory. They were usually modified soon after delivery to use a lead acid type. . .Are the nicads a better option for the colder/temperate climates?

BTW, I think you will find the starter contactor is behind the hat bin on the RH side of the A/C. The battery and external power contactors will be in the nose. <img src="tongue.gif" border="0">

Has anybody proved/disproved the theory that if you crack the throttle during start while the N1 is still accelerating, that it will start better? . .The original start procedure was to let the N1 peak with the starter before fuel was introduced. The argument against this was that the N1 turbine lost its acceleration momentum and needed more fuel/TOT to maintain its starting schedule.

heli
24th Feb 2002, 13:14
H122,

Another possibility could be the starter gen, if it has badly worn brushes, or a duff commutator. Allison specifically require the throttle to be opened between 12-15% Ng, I have never subscribed to the technique of letting the Ng peak. Too much chance of no ergs left in the battery to properly spark the ignitors and give a clean start. I had Nicads in some 206's I operated, and haven't found much difference with lead acids, except a run of Sonneshein (sp?) units when they couldn't crank as advertised. Switched to Hawker batteries last year, and no further problems.

One 206 I fly has the fastest spin up of a C20 I've ever encountered, crack the throttle at 12% and it's past 15% before the fuel lights off! All other parameters are normal, it's been the same for years, even after a mini.

I'd be looking at the battery contactor in the nose, reckon Steve had the right idea there.

TeeS
24th Feb 2002, 13:27
Beware holding the temp too low during the start. As I understand it, during the early stages of the acceleration there is not sufficient air flow through the engine to 'shape' the flame, hence even though it appears to be a nice cool start you can be 'torching' the combustion can. A start that keeps the TOT towards the upper end of the limitations is preferable to a long slow one. That's my understanding of it anyway!

paco
24th Feb 2002, 14:05
I regularly use the technique put out in the Allison letter (sorry don't know the reference) which essentially is, as N1 accelerates through 12%, crack throttle (our machine likes 13% better for some reason), and accept slightly higher peaks. I can't prove this, but I do feel it gives me a better chance of starting in remote areas because the battery isn't worked so hard during its life.

phil

tgrendl
25th Feb 2002, 21:45
Hone 22

I think that statistically most engine failures happen within 100 hours of rebuild/reman. If the aircraft went in without the problem you mention and came out not quite right it's a cause for concern.

You mentioned you had light off but no increase in N1 at all.

During the start attempt did the gages fall to zero? For a 206 this is a last chance indicator of bad battery.

Did the health checks for that engine (and topping check) after rebuild show the engine as positive and staying or was it rapidly decreasing in performance?

Lots of variables to look at here but don't let safety become one of those variables. Best place to find something wrong is on the ground.

Let us know what's found please,

Thanks

paulgibson
26th Feb 2002, 03:50
tgrendl

Can you explain what you mean by a 'topping check'. I understand in a 212/412 OEI situation to check max N1, not so sure what you mean in relation to a 206. Pretty sad old compressor to 'top' a 206 though......

cheers

b407driver
26th Feb 2002, 09:52
Doesn't anyone want to ask whether he's flying a B-model or an L-model? I assume a B-model, but many of the posts reference correct answers for one or the other model...

Just a thought!

sprocket
26th Feb 2002, 13:09
I've assumed a 206B, because of the ceco system that was mentioned in Hones first post.

Hone22
26th Feb 2002, 13:28
Hi all,

yep, a 206b model and problem was traced to a shagged battery (more volts Igor!!)

Thanks to all who contributed, I'm sure others as well as myself are now more enlightened and once again the whole reason for this forum is to share the wealth of knowledge out there so mistakes aren't repeated endlessly.

Actually other reasons for this forum inlcude telling big whoppers, shooting the breeze, where is xxxx i flew with in 85' ..........Keep it up.

Any more pearls of info re- B206b greatly appreciated.

Cheers & flysafe. .Hone :) :) :)

BlenderPilot
27th Feb 2002, 22:12
In the 206 JRIII the XMSN limits are as follows:

30 PSI Min. - 70 PSI Max.

and

30 - 50 PSI Continuous operation (green arc)

That leaves a "black arc" between the end of the Green Arc at 50 PSI and the Max 70 PSI.

My pressure has been constantly in that black arc recently, and since it is still below redline I'm not sure if it's allright. I can't find any info on what to do if this happens.

any suggestions?

thanks

lills
28th Feb 2002, 13:59
Mexicano,

I have had that problem in the past. When mentioning it to the engineers they did not seem to concerned, but they fix the problem in 2 minutes.

There is a screw and locking nut on the top of the xmsn on the port side it is only a matter of adjusting that and running to check the pressure. Wouldn't recommend you do it yourself.

Hope that helps.

tigerpic
28th Feb 2002, 15:21
your specific question was answered... but i want to add something in general. when you fly any (!) helicopter under normal conditions, you will have the normal indications and performances. if something unusual happens, even though it is within the specified limits, i would be concerned straight away, like you have been with your question. there is no black&white in anything, e.g. your helicopter will not explode if you pass go to 111% torque.

i have two happenings to me where the helicopter was within limits, but indicated something very wrong: the first one was a reciprocating engine that was almost, but not quite, showing red line on the cyl head temp. the owner was interested in all the people waiting to do rides, and told me to continue flying. i was within limits, but the helicopter ended up with loosing horsepowers and thus decreasing performance in general. the second was a turbine, where one of the bearings were leaking. the leak was within limits of what the manufacturer specified, but the helicopter flamed out in flight after internal engine failure as a result of engine oil being dumped into the burner can.

this is scary! a helicopter pilot should have good knowledge of the aircraft, aircraft systems, the instruments and their interpretations, etc. i have met many pilots who had flown lots of hours on machines that they could not understand the instruments and how to interpret combining several instruments and/or indicators (e.g. b206: fuel pressure on 0 but no fuel pressure light)

the other side is being too cautious, sacrifying a mission (and lots of money) for nothing. a former colleague of mine made an pre-cautionary landing on an airport away from the base, because he had a generator failure - instead of shutting down unnecessary equipment following the poh, he delayed the return with several hours, had to start the helicopter again, and fly the helicopter back to base. this because he did not know the pilot operating handbook. for that reason, i do not blame him for landing. <img src="tongue.gif" border="0">

BlenderPilot
1st Mar 2002, 06:15
Thank you very much!

¡Muchas Gracias!

MaxNg
2nd Mar 2002, 01:49
Mexicano

30 -50 psi Green arc = Normal operating range. .51-69 psi AMBER arc = Cautionary range . .70 psi = Red line max

the colour coding is to give you a " at a glance " indication

regards

<img src="redface.gif" border="0">

[ 01 March 2002: Message edited by: MaxNg ]</p>

widgeon
2nd Mar 2002, 03:52
Do you need to pass colour blindness tests ?.

Grisoni
19th May 2002, 05:40
Does anybody know if the high altitude tailrotor is worth the $$ ? We're flying at anywhere from 4000' to 8000' usually at @<hidden> 4000#. Thanks.

Forgiveness is easier to obtain than permission.

Dunhovrin
11th Oct 2002, 14:59
I'm finally getting around to adding a Jetranger to my license. Does anyone out there know of a good source for tech (ie ground school) notes?

Arm out the window
15th Oct 2002, 12:01
I was looking for the same thing myself re the Jet Ranger; this site covers one of the military variants but has got a heap of good generic info in it all the same:

http://www.lsirucker.com/TECH_LIB/Operators%20Manual/operators/TH67_Main.htm

Keep us posted if you come up with anything else useful; good luck!

Randy_g
17th Oct 2002, 03:00
If you can find someone who has taken the Bell course, they may have a 206 transition manual. It is an incredible source of info on systems. If you can get one, I would highly recommend it, and I can't think of a better publication (although there may be, but I haven't found it) for someone moving onto the JetRanger. Unfortunately Bell doesn't sell it on it's own. :(

Cheers

Dunhovrin
19th Oct 2002, 11:54
Thanks chaps. I'm wading my way thru the TH-67 manual.
Ta again for the the heads up

Arm out the window
20th Oct 2002, 10:03
You're going to have to change your nickname now, Dunhovrin!

Dunhovrin
24th Oct 2002, 16:39
From now on I wish to be known as:

ThepilotformerlyknownasDunhovrin

(that is assuming I get my s**t together as start rotorvating this side of 2099....)Once again thanks for the US Army link - SiryesSir.

widgeon
22nd Nov 2002, 11:21
http://www.rotorhub.com/news/0211/bell-1.htm

Good to see there is life in the old girl, I will not ask the obvious question.

BlenderPilot
23rd Nov 2002, 01:39
Over here the Mexican Agency in charge of erradicating drug plantations purchased 27 brand new 206L4's two years ago, they are mosty used for spraying pot up in the mountains, I got to ferry some of them from the factory to Mexico City, and since some of them came with the the Simplex "Jacuzzi" and were armored, they were slooooww.

M/V
26th Nov 2002, 05:28
Can anyone tell me what are the major differences between the L3 and the L4 which enables the higher max. gross weight i.e 4150 lbs v 4450 lbs. They both have the Allison C30P. Is it a reduced TBO on the L4 (more power that can be pulled = more frequent inspections of gears etc) ? Thanks, regards M/V

sprocket
26th Nov 2002, 11:48
Just trying to remember, the L4 had a thicker skin on the tailboom, a different FWU, a Kaflex main D/shaft, and a transmission with a "406" part number.
The T/R g/box may have had a different P/N as well.

Brother
26th Nov 2002, 13:52
Don't know what the exact differences are but Airlog will be using these aircraft in Escravos, Nigeria in a mix with Bell 407s. The original plan was to have all 407s but it was decided to mix the fleet due to 407 reliability issues.

Brother

BlenderPilot
27th Nov 2002, 16:54
one thing is for sure,

I fly both very often and the only very important difference I program into my brain before each flight is the following:

Over here at altitude (L4's w/no High Alt. Kit) you will run out of left pedal a lot sooner than you will run out of power (TQ, TOT, N1), learning this has many pilots around here to some nasty surprises. With the L3 if you watch your wind you'll run out about the same time you reach both limits.

I remember there was this really tall building I used to fly out of with a TV crew, and somedays the thing would hover IGE about 12 inches from the ground with 75% TQ, but the left pedal would be almost all the way in, any increase in power would start the nose going right and no pedal to stop it, so in order to clear the pad you had to start pulling pitch 180 deg. from the desired exit, the L4 would climb as it yawed right with the left pedal all the way in, then as I reached the desired heading being now 20-30 feet high, I would lower collective slightly to stop the yaw, and push collective forward until I had some airspeed, needless to say that the aircraft that when the aircraft sank I now had plenty of altitude to clear my tail from the edge of the building.

Returning to the pad heavy was a completely different story, but I guess easier since it requires less power to land than to take off, but you had to have the wind help you.

jellycopter
15th Feb 2003, 09:27
Can any Rotorheads out there help me please. I am looking for info on performance for the Bell 206B3 Jet Ranger compared to the Bell 206L3 Long Ranger. The task I have in mind is in Africa so hence the Bell selection as spares and maintenance are achievable. Ops at SL upto +1500' at 30 to 45 degs C. Need to carry 3 to 4 pax plus pilot and have fuel for approx 1 hour 30 mins. Aircon essential for pax comfort, although I assume it could be switched off for T/O and landing - therefore just a weight penalty. Also ideally have light-weight floats fitted but not always essential - another weight penalty. Can the B3 do it, or do we really need to fork out the extra expense of an L3? Any views welcome and anecdotal experience invaluable. Thanks in advance. J

B Sousa
15th Feb 2003, 15:05
Having been to that part of the world and having flown both those aircraft for many years I can say the difference is day and night. What your asking is on the upper edge of the B206B3s performance and within the capabilities of the B206L3. You may be able to sit down with the numbers and say yes it can be done with the B3, but when you get out in the field and catch that extra gust on your tail rotor and watch the Tq meter wrap around a couple times, it then becomes clear.
Thats in a bare bones aircraft. When you add on floats, A/C and four construction workers, your leaving at max gross.......THEN you have to work.
Yes I believe the extra expense of an L3 would be worth it. You will also have to crunch numbers with an L3 but will have much more to play with.
Pose this on the African Forum and see what some others say.
If you hit the Lotto in the meantime look at a B407. Having recently flown that one, it will really make you smile.
If your going to invest, invest in safety.
Good Luck
My email address works.

Devil 49
15th Feb 2003, 22:24
Have to second Jellycopter-the B3 is on the skinnny side of marginal as proposed. Yes, it'll do it the job if everything's ideal-but only just. If you can live with compromising on your requirements (like limiting max gross by a couple hundred pounds) versus cost, the B3 is an economical choice. If that's not an option, the L3 is better choice-it's got so much more capacity versus what you propose, that it would be my first choice as a pilot-and I don't like flying LongRangers-cramped, wiggly and CG requires more attention (still very simple).
The L3 is the workhorse of the pair proposed.

jellycopter
16th Feb 2003, 09:06
Thanks fellas. Much appreciate your replies. I'll just have to explain to the boss-man that he'll have to postpone the new Ferrari for a couple of months and spend a bit more on his chopper! Thanks again. J

Ascend Charlie
16th Feb 2003, 09:18
Further confirmation on the L series - agree with all the comments above.

We operated 206 B2 and B3 alongside an original L - which has a C20B and water methanol injection for takeoff. Even though it was the same engine as in the B, it was able to go faster (better area rule), flew smoother (nodamatic versus crappomatic) and allowed more space in the back.

Move up to an L3 or L4 and it leaves a B3 in its wake. Your boss might prefer a B3 for his wallet, but his customers / passengers will be very cramped in the back, especially the centre seat with 3" less headroom and a transmission tunnel" under his feet. The L3 has these too, but with your passenger load, nobody is inflicted with the centre seat, as long as he doesn't mind going backwards.

B Sousa
16th Feb 2003, 13:04
As to the L3 vs. L4. Yes the L4 is even better yet, BUT I think you can get a clean L3 on the market today much cheaper than a comparably used L4.

jellycopter
17th Feb 2003, 07:36
Once again, thanks fellas. I fly to the USA today to inspect a few L3s and hopefully do a deal (subject to in depth engineering inspection of course). Thanks again! J;)

Buitenzorg
17th Feb 2003, 18:26
One other option you should keep in mind is the L-1 re-engined with the -C30P engine. Quite a few were thus modified by PHI amongst others. With the upgraded rotorhead (they nearly all have them) the max gross weight is identical to the L3, performance is identical, the fuel capacity is a bit lower but no problem for what you propose. They'll be available at good prices.

The modification was brought about by problems with the -C28 engine, especially but not limited to, high DA situations.

B Sousa
18th Feb 2003, 11:20
Good Post by Buitzenzorg. I even forgot that I had flown the B206L1/C30P long before I flew the L3. Basically the same thing. It certainly would be a choice for purchase in the utility scene.
I think the only real difference would be some ADs to the L1 tailboom that were factory correct on the L3?? Correct me??

Buitenzorg
18th Feb 2003, 18:33
Spot on, Bert, but no biggie.

Most L1's have an AD (I believe it's AD 96-18-05) requiring a visual inspection of the tailboom in the areas around the posts for the Dzus fasteners of the TR drive shaft cover, to be done every 50 flight hours. The L3 (and L1's that had the tailboom replaced) have different type posts and don't require this inspection. Including shut-down, start-up, removing and replacing the cover, and the actual inspection itself, it would usually take just over a half hour to complete.

Hilico
23rd Feb 2003, 00:07
Ascend Charlie talks of a transmission tunnel in a B206 "beneath his feet". Is he not getting confused with a Morris Oxford?

Ascend Charlie
23rd Feb 2003, 08:06
Morris oxford?? You must be as old as me to remember them. In fact, my family owned one, and it had a serious tunnel.

No, in the 206 it is a safe haven for some cables and pipes, and is about 1-2" high. A bigger obstruction in the 206 centre seat is the broom cupboard, which takes away about 4" of kneeroom.

And don't bother asking me if I am now confused with the janitor's room.

paco
25th Feb 2003, 11:44
Have to second the C30P - the temp needle doesn't even come close to the yellow!

phil

Hippy
20th Mar 2003, 03:01
Hi rotor heads. Was working a jet-ranger on 135.15 this afternoon, doing some flight checks near Brize Norton. Nothing unusual there, but this guy requested a climb to FL200. Caused a bit of a stir in the radar room, "schurly some mistake", we thought. Anyway, said chopper got to FL200, after a while, did his stuff and went back down.

A quick Google has revealed some sites quoting 13,500ft as service ceiling, others 20,000ft.

My questions - Pressurised cabin? Oxygen needed, or not up there long enough? Any precautions taken against hypoxia / nose-bleeds? Why 2 different stats on the web, different marks / variants? Can I have a go (only live down the road)?

Anyway, gave us something other than airspace changes and wars to talk about.

Cheers,
Hippy.

407 Driver
20th Mar 2003, 03:09
No problem for a JR to be there, big problem for a pilot though. The JR is certified to 20,000 below 3,000 lb, and to 13,500 ft at AUW of 3,200.
I have had a JRII at 16,500. It was still climbing well and flew well. Why? who knows, I was young and foolish?

http://www.bellhelicopter.com/aircraft/commercial/spec_206b-3_detail.html

talkturn
20th Mar 2003, 09:55
B206 @<hidden> FL200 - no real problems

no requirements for pressurised cabin but oxygen required. (2 litres per minute from FL100 to FL180 and 4 litres per minute above - roughly)

TOT (turbine outlet temp.) is usually the limiting factor

The Jetranger can get much higher

Happy Landing !
20th Mar 2003, 11:43
No Sweat, 20K for the JR - Easy.

Need oxygen though.

Hippy
20th Mar 2003, 12:31
Thanks all for the replies, very interesting. Would the O2 be plumbed-in to the aircraft, or are we talking personal bottles as used by mountaineers? Any type of CAA certification for O2 supply?

Curiosity killed the cat, but it's good to learn new stuff and always a good idea to know exactly what air crews are having to deal with.

Many thanks,
Hippy.

talkturn
20th Mar 2003, 15:42
oxygen tanks and not plumbed in I guess

BlenderPilot
20th Mar 2003, 16:26
Trust me, going up to 20,000 in a JR is NOT easy, sure it under ideal circumstances you might make it up there, but in a large number of instances it won't get even close, in any case getting up there could take forever.

Just last March 1st I went up to take picutures if the "LMT" (Large Millimeter Telescope www.lmtgtm.org) which is on top a 15,000 FTAMSL mountain, which is next to a 18,400 FT volcano, JRIII, +4%TQ powercheck J engine, 1 Pax, 33 Gallons, and OAT Zero degrees celsius, ISA +15, my results were not more than 50 KIAS Max, Max Cont Pwr, and not an inch above 15,500, it would just not climb anymore.

Anbody tells you it can easily go to FL200 has problably never done it or has done it under optimum circumstances in regards to GW, ISA, etc.

Pictures of the LMT below, the volcano next to it is the "Pico de Orizaba", 18,400 FTAMSL.

Oxygen? perhaps, but here's a thought, Peruvian AF pilots who fly over to the Peruvian Andes routinely would have a big grin in their faces if you told them you needed oxygen for a short flight up to 20,000

http://homepage.mac.com/helipilot/PPRuNe/LMT5.jpg

http://homepage.mac.com/helipilot/PPRuNe/LMT4.jpg

B Sousa
20th Mar 2003, 18:45
Certainly nice pictures. Makes me want to see someting of Mexico other than TJ or Rosarita beach.
I think the Regs have something to say about high flights. At least here in the states there would be a mandatory requirement for Oxygen and if my airspace memory serves me, I do believe the Aircraft should be filed as IFR. That would also require the aircraft to be IFR equipped. Expensive in a B206. Interesting to find out if someone gave this guy some heartburn over his flight.
Sounds like a fun ride down though....

BlenderPilot
20th Mar 2003, 20:44
You are right about the oxygen requirements I'm sure it is legally required, but still doesn't mean it is used, you know how it it is in most countries.

If you want to see a little bit more of Mexico (city) here's a link to my Mexico City from a Helicopter pictures webpage, all the pictures were taken by me while flying around the city.

Mexico City from a Helicopter (http://homepage.mac.com/helipilot/PhotoAlbum3.html)

CyclicRick
20th Mar 2003, 22:40
A jetranger at 20k? in free air? up a mountain I can JUST understand but....:eek:
I get nosebleeds at 2000ft never mind 20,000ft.

Are there any other heli pilots out there scared of heights?

offshoreigor
21st Mar 2003, 00:23
Above 10,000 up to 12,500, limit 30 minutes no O2. Above that, O2 required. Thems the rules!

Cheers, :eek: OffshoreIgor :eek:

talkturn
21st Mar 2003, 09:51
back to blender

no expert but at 15500 ISA+15 - does that mean you are at about 17300 density altitude.

And if so your TAS is nearly 70kts which might be a reason for poor climb.

Any ideas??

Top photos and nice day for it

BlenderPilot
21st Mar 2003, 14:18
TalkTurn, Good observation.

You are completely right! DA was at about 17,300 and TAS was something like 70 KTAS when at 50 KIAS, but I tried different airspeeds below that and it seemed that anything less than that would only start me down.

Actually now that I remember I was laughing about it with the photographer, I found the spot where ANY change in my Power, Attitude, Airspeed or the slightest down draft would make the helicopter start down vigorously, it was at its absolut limit, felt like hanging by a very thin thread, funny feeling to not be able to climb an inch more.

Wonder what the autorotation caracteristics would be at that altitude, I guess it would have pretty much the same qualities of a flying red brick.

Shawn Coyle
21st Mar 2003, 15:20
Blender pilot -
Just out of curiousity, what condition were the rotor blades? Old, new, pitted, etc? The engine might well be above spec, but if the blades aren't working well you won't get the performance out of the machine.
Also, was the torquemeter recently calibrated? Again, it might be denying you power.
But a friend of mine also added that somewhere around 20K, the rotor just stops working very well - he saw it in some Army testing in the OH-58 in the 70's.

crab@SAAvn.co.uk
21st Mar 2003, 17:52
Hippy, did you note the callsign of the jetranger? If it was a Tester callsign it may well have been a Boscombe Down student Test Pilot crew carrying out high altitude handling exercises. They used to use the Gazelle I believe but if it is u/s they might well rent a 206 for the TP course to use.

BlenderPilot
21st Mar 2003, 17:54
Shawn,

Never even crossed my mind to think about the blades, but it´s a pretty interesting point.

I just walked out to the helicopter and looked at the blades closely, they look good, not much erosion or even paint missing actually they look new but they have that 3M tape over the erosion strips and that might affect performance, also they might have been very dirty when I went down there, this helicopter gets about 40+ hrs. per week and doesn´t get washed as often as it should.

Good observation, thank you.

Hippy
21st Mar 2003, 18:08
Thanks again for all your replies / photo's etc. Glad I seem to have started a good discussion also.

crab@<hidden>
No, not ETP. It was British civil registered out of Denham. Not proper to put full c/s here and I can't remember it now anyway.

:D Hippy.

CTD
22nd Mar 2003, 21:26
Mr. DM of Trans North in the Yukon is one of the highest time mountain pilots in Canada. He received an award this year from HAI.

There, he told me a story of how he was attempting to put sling loads at 19,200 ft with a 350B2, but could not. He came back with a 206BIII and completed the job.

Shawn, you know our friend Mr. AR from BHTC - his Himalayan rescue of a Pakistani Lama crew from approx 21K in an L4 is one of the highest ever. He left the crash site with 5 souls and 300 lbs of fuel if I remember correctly.

BV

407 Driver
23rd Mar 2003, 05:48
Hey CTD, I understand that DM has a C20R installed in that 206. He sure did well up in the 19,000's with that aircraft.

Shawn Coyle
24th Mar 2003, 23:04
to CTD:
Yes I remember AR from BHTC. Quite the feat to do that. I remember him saying that he got out of the helicopter to get the photos of the event, and nearly blacked out from lack of oxygen. There's a reason for those regulations!
I believe there was a higher rescue somewhere on Everest a couple of years later.

CTD
25th Mar 2003, 02:59
Shawn - yes, the picture clearly shows the Lama on its side, and Alain's jacket on the ground next to the ship. The pilot door is ajar as well...

Big chance to take, getting out in the snow on top of the world, but the photo was worth it!

BV

407 - R engine or not, he's the man...:D

Happy Landing !
25th Mar 2003, 17:36
Hippy did say in his opening gambit that the machine "got to FL200, did his stuff and came back down"

Hippy was working the radar so he must have seen it do the job!
Hence - It will certainly get to FL200

Happy Landing !
5th Jun 2003, 22:49
I was unfortunate to have an in-flight engine fire on a B206 last Saturday.
There were no indications from the T's & P's, and on landing the fire worsened, presumably because power was being reduced. It got even worse when I shut down to flight idle.

It now transpired that a Turbine seal had given up, allowing oil from the header tank into the combustion chamber and therefore igniting.

I was informed that if the flight had continued for another 10 – 15 minutes, the Donkey would have stopped due to lack of oil.

For future reference, apart from low oil pressure, high oil temp, what other symptoms would/could there have been to have warned me?

I did'nt have any idea of the circumstances until ATC came on the blower !

Happy

Shawn Coyle
5th Jun 2003, 23:46
Without a fire warning system, probably no other symptoms.

handyandyuk
6th Jun 2003, 04:57
Without a fire warning system I'd imagine you're limited to external observation by others prior to the donk dying.

As I started my PPL a few years back we had a double belt failure on a 22 resulting in the oil cooler pipes getting sliced. The only indication of the resulting fire was the reflection of the flames on the apron concrete. According to the tower, there wasn't much in the way of smoke.
The AFS chappies (wonderful guys) tell me it's rare to get much smoke due to the big fan on the roof rack...fair point. So short of a heat sensing system monitoring the interior compartments, the most likely indicator I should imagine would be low oil pressure followed by overtemps and then the big quiet bit.

But I'm no expert... so as someone who only flies a 22 now and then (also no fire warning) I'd be interested in the knowledge of others, myself.

sprocket
6th Jun 2003, 05:20
If you have some reason to suspect a fire, do a turn or two. You may then be able to see your own smoke.

I heard of an incident some years ago where a 206 had oil leaking on to the outside of the turbine casing. The pilot saw his smoke shadow on the ground. (Obviously was not flying too high at that time)
He did a couple of turns and confirmed the shadow was not an optical illusion.

PPRUNE FAN#1
6th Jun 2003, 05:47
sprocket wrote:

I was unfortunate to have an in-flight engine fire on a B206 last Saturday.
There were no indications from the T's & P's, and on landing the fire worsened, presumably because power was being reduced. It got even worse when I shut down to flight idle.

It now transpired that a Turbine seal had given up, allowing oil from the header tank into the combustion chamber and therefore igniting.

I was informed that if the flight had continued for another 10 – 15 minutes, the Donkey would have stopped due to lack of oil.

For future reference, apart from low oil pressure, high oil temp, what other symptoms would/could there have been to have warned me?

Well.......you didn't exactly have an "engine fire" now, didya? That would be characterised by open flame in the engine compartment but outside of the engine, no? What you evidently had was an internal seal that let go that let a bunch of oil get into the combustion chamber to burn with the fuel. Probably made a great steaming gobs of white-ish smoke that must've looked bl**dy awful but in reality wasn't a "fire" and posed no immediate threat or danger to your poor 206. ...Until the oil ran out, as you noted. But at that point the source for the smoke would also be gone.

Although we all probably feel apprehensive about them, engine fires in turbines are not generally a cause for worry. Sure, fuel lines can break, and fires have happened, but they're rare. Even if a fuel line broke and sprayed fuel, there's really nothing in the 206 engine compartment to ignite it (it's Jet-A after all). Furthermore, most of the mechanical failures that could cause a fire would likely cause the donk to quit pretty quick anyway, so the big bang would probably be your first indication.

In the unlikely event of a real engine fire (ask the early 206L-1 pilots), you'd have to be on the ground very quickly indeed before the aircraft was so consumed that controllability was lost.

Dantruck
6th Jun 2003, 07:24
You really must get yourself a girlfriend:suspect:

BlenderPilot
6th Jun 2003, 11:47
There are also several indications of this described malfunction, the most obvious one would be that if you are burning extra oil in the combustion chamber your TOT (turbine outlet temp.) is very likely to rise considerably! You are also going to lose oil pressure quickly, and more so if it is burning at a rate that will consume 5.2 liters in a few minutes, like described!

I guess it could be argued by many if this was an engine fire or not, my opinion is an engine fire is when there is fire in the engine compartment.

Shawn said if you had a fire detection system you would know? but most engine fire detection systems are the "melting wire" type running inside the engine compartement that turn on the light in the cockpit, but how is that going to work with the engine burning oil internally? Even if you had the engine fire detection kit you could probably not get warning, so is it an engine fire or an engine burning oil?

Happy Landing !
6th Jun 2003, 17:12
OK - Engine burning oil. Tell that to the Firemen who turned up and wanted to put the flames out, or tell that to the CAA bloke who was in receipt of the M.O.R !

Oh I see - Sorry.

Because the whole bloody thing did'nt go up in flames it's not a fire, Right.

Next time I'll jump out and throw a few gallons of fuel on it.


:ok:

Ascend Charlie
6th Jun 2003, 19:54
This is unusual - I agree with something PPF#1 has said! One of us has changed!

Yes he is spot on. It ain't an engine fire - the engine is behaving relatively normally, albeit with a lot of oil going down its gullet. If there was a fire detection system on a 206, it would not detect anything in this case, and if there were an extinguishing system, activating it would achieve absolutely zero positive results.

You were lucky to have somebody tell you about the smoke, and it saved you the stress of the oil pressure failure and the eventual engine seizure - instead you had a Happy Landing. Buy the controller a lottery ticket, and get one for yourself.:8

sprocket
6th Jun 2003, 20:01
quote:
--------------------------------------------------------------------------------
sprocket wrote:

I was unfortunate to have an in-flight engine fire on a B206 last Saturday.
There were no indications from the T's & P's, and on landing the fire worsened, presumably because power was being reduced. It got even worse when I shut down to flight idle.

It now transpired that a Turbine seal had given up, allowing oil from the header tank into the combustion chamber and therefore igniting.

I was informed that if the flight had continued for another 10 – 15 minutes, the Donkey would have stopped due to lack of oil.

For future reference, apart from low oil pressure, high oil temp, what other symptoms would/could there have been to have warned me?

Did I really say that?? :ooh: :uhoh:

PPRUNE FAN#1
7th Jun 2003, 00:54
sprocket actually did write:Did I really say that??Oops! Sorry, shprocket. You're right, it was Happy Landing ! As my kids say, my bad. My face is red.

To Happy Landing ! and Blender: I actually did have a similar bearing failure while hovering out for departure in a ship equipped with two C-20B's and did not notice anything unusual with the TOT gauges. The fire-warning lights were dark. Over the radio came a surprisingly calm message, "Hey boss, you're on fire," which everybody onboard heard of course because they all had headsets. I looked down at my shadow, saw the plume, knew what it was and put her down. As soon as I stopped the forward motion the smoke caught up with us and we were enveloped in a white/gray cloud. Man, you should've seen my pax un-ass the a/c. They jumped out like it was on fire! They ran away a safe distance then looked back, astounded that I hadn't leapt out too. But hey, the good engine still needed a two-minute cooldown. No sense screwing up both of them.

Happy, you got lucky. In the first place it wasn't a "fire" (i.e. no danger of airframe involvement) despite what the firemen thought. In the second place, you were notified early enough that you didn't get to perform an actual EOL. Count your blessings.

John Bicker
7th Jun 2003, 03:14
To be clear:

Internal oil leak in the engine? Love to know which one for interest. The seal must have come apart big time. I seriously doubt that you will see any noticeable change in the TOT. I have run all of the allowed fuels in a 250 and never seen any difference.

As for the T & P's. It is a fallacy that low oil quantity will give you a high oil temp. Simple physics tells you that with LESS oil it goes via the cooler more in a given period of time, so lower temp. Applies the same on piston engines as well. By the time the pump runs dry there will be no oil in the return line to show you the temp.

Classic is the B 206. People don't read the manual and fill the MGB till there is a bubble at the top of the sight glass. WRONG! Full is halfway up the sight glass. Fly a 206 hard at high temps (firefighting)and watch the MGB Temp approach the limits - solution - remove oil until it is just visible in the bottom of the glass. No more problems.

Ascend Charlie
7th Jun 2003, 14:14
Saw a case when the 206 MGB was overfilled and the oil frothed and the pressure dropped way below limits and brought on warnings. Same fixit, drain out the extra oil.

Hingeless Rotor
9th Jun 2003, 10:05
As far as I am aware the oil does not get circulated through the cooler in a separate faster cycle, so why would the temp be lower if the oil is also going through the engine at a proportional rate to the cooler? If all the oil is not being burnt as it arrives at the engine then I believe you will see a negligible overall effect to the oil temperature until the oil level is too low to draw up.

The point you make regarding the transmission oil temperature is irrelevant to what was going on in the engine. Not sure why you put that one in. I presume it is because of your figjam approach to discussions.

I too have had the oil exit a 206 in flight. The only indication I had was fluctuating oil pressure when presumably the oil level reached the pickup in the tank. There was a corresponding increase in oil temperature from that point on.

Cheers
:hmm:

NickLappos
9th Jun 2003, 10:33
The internal oil seal failure is actually a very very bad thing to happen, even if the oil never leaves the engine. Here's why:

The oil enters the airpath and gets misted into the fuel/air mixture. It burns, and adds its energy to the situation. This does not cause the tot to run hotter, because the fuel control cuts back the fuel to exactly the right proportion to maintain proper N2 rpm. This means that you save gas because you are burning oil instead. So far, no sweat until you run out of oil.

But if the seal gets worse (they always do) then the oil leaks faster, and then faster. If the oil leak gets to be as much as the fuel flow should have been, then the fuel control will cut all the way to idle. If you lower the lever or if the oil leak gets worse, than the engine will run away, and the overspeed protection will be no help at all (it will cut the fuel, but that's not what is burning!

This has happened, and it usually leads to an explosive runaway, where the engine comes apart.

bellsux
10th Jun 2003, 14:31
You haven't said which seal failed but if it was your #5 bearing seal that gave up (most likely) you would have had no increase in temperature indications as they are downstream of the TOT probes. When you wound it down to ground idle the balancing air would have been reduced and allowed even more oil to pump past the seal making the smoking worse. Other factors to look at was the seal showing any indications on flights prior to yours that it was U/S (when it usually is on it's way out produces a large smoke puff on shut down and smoking on start). You did say it was a turbine seal but if there was a small increase in TOT it could point to the #1 bearing leaking but it would be so small you would not be able to notice the rise anyhow.
Technically is was not a fire but a bearing failure but the fire fighters did the right thing as when they see smoke they think fire and you are lucky that they were there just in case something worse happened. If you did run out of oil things would have turned really nasty really fast, caution panel would have lit up like a christmas tree.. oil temp, oil pressure.. perhaps chips as bearings failed, oil pressure guage fluctuates with cavitation in the pump then falls, nasty noises as donk lets go and top it all of with an auto with eng horn blaring and eng fail light glowing a lovely shade of red... that's if your donk's wheel hasn't chopped your blade in two.

vorticey
10th Jun 2003, 22:34
wouldnt 'simple physics' say that the oil cooler only cools a % of the total cooling effect? the reservior is an oil cooler and so is the crankcase. surly more oil in these should make cooling an easier job.

i know nothing of this MGB (main rotor gearbox i prisume) but is it possible the temp sender doesnt get enough oil splashed onto it to read corectly? with more oil in the sump of anything, more heat can be transfered to the outer case and to atmosphear.

sprocket
11th Jun 2003, 05:32
vorticey: It is a known symptom with overfilling 206 T/Ms.

As the oil is not stored in a separate tank, the higher oil level in the T/M enables aeriation/foaming to occur (it gets stirred up by the gears).
The efficiency of the pump is reduced because it is pumping a lot of air and also a lot of oil can get vented overboard (and for some reason most of it does when the level starts off way too high).


Nick: it all depends (as bellsux said) on where the leak is …

If the #8 brg seal (labyrinth type) or its sump leaked oil, it would be closest to the combustion.
It would burn but not “efficiently” as it has not been “atomised” by the fuel nozzle or being mixed to some extent if coming from a compressor bearing .
I suspect that if it were a significant leak, it would give a higher TOT indication without performance increase.

vorticey
11th Jun 2003, 18:25
thanks sprocket, its good to know the reason behind things

Happy Landing !
12th Jun 2003, 02:35
Well Thank you One and All....

The ship had just had a star annual (3.5 hrs total flown to "Seal malfunction").

The Hot section has now been removed, and it was the 5th wheel bearing.

Absolutly no indications in the front, and no smoke on startup/shut down that I noticed.

It was planned that day to pick up another Pax rotors running, then head off to the Breacon Beacons for some fun !

Judging by what has been said here (Thank you), I should have got a lottery ticket that day.

Ah well, back to the R44 for a while

Happy :ok:

NickLappos
12th Jun 2003, 11:29
sprocket,

If the leak gets into the combustion section, it will burn, and when it does, it replaces fuel. This is a classic engine runaway scenario. Another way to make your engine go this way is to leak any conbustable into the inlet. This is what happened to the V-22 that shattered an engine over the Potomac. A leak built up in the inlet, and when the engines were tilted back, the fluid poured into the engine, causing a destructive overspeed that was unpreventable with the normal overspeed shutdown.

A typical Allison burns about .5 lb/hr/SHP, so if it were at 65% power, about 200 HP, it would burn 100 lb/Hr. That is 16 gallons per hour, or 1 quart of fuel a minute. If the engine starts leaking at 1/2 quart per minute, and the pilot lowers the collective to descend at 25% power, the engine will run away and probably destruct.

Ascend Charlie
12th Jun 2003, 18:15
Nick - I wonder why this sort of info isn't readily available??

I have been flying turbines for 34 years now, and this thread is the first time i have ever seen this information. A bit scary that "shutting down" the engine will have no effect and it will burst its breeches with a cloud of dust and a hearty "hi-ho Silver".

It should be taught in any turbine ground school. I have done the Allison school a couple of times and they didn't talk about a major internal leak at all.

A marketing opportunity for Shawn Coyle and a new book!! I will take my usual 10% thanks...

Bladestrike
12th Jun 2003, 18:22
Exact thing happened to me in a 206L-1 in the early eighties. There was no indication of anything wrong in the cockpit, but billows of black smoke were pumping out of the can. With no place to land (Northen Quebec) I flew for a few minutes before finding a clearing, and actually started to see a lowering oil pressure prior to shutting her down. It makes for a very long few minutes when you know something bad is going to happen very shortly and you're over nothing but trees.

John Bicker
12th Jun 2003, 21:29
AC,
Get your hands black Rob with all that spare time, Stud won't mind. Ask him about the early days of the C30 engine in the A model and why thay had large lumps of steel inside the engine cowlings.

To go back to my original post - I still think that as HL said " the T & P's showed nothing abnormal" and with the proviso in this case until it actually ran out of oil there is no reason to.

As to the claims of higher TOT in this case as we now know it was downstream of the thermocouples so there would be no indications. As to the higher TOT claims with oil leaking in before the thermocouples - why? This is a heat engine, if you release x kJ of energy you get what you pay for and the temperature would remain the same. The flow would change in the FCU to remain at the same output because the engine cannot do something all of a sudden for free, the efficiency of the engine doesn't change. The heat value may vary slightly from one fuel to another but the amount of energy released must remain the same so it may take more or less fuel/oil. In the case that NL makes the fuel, in this case oil, is uncontrolled. Yes it will come apart.

The oil system in the Allison is sensitive to any abuse from the operator and the mantainer. The 6 & 7 bearing areas can suffer from lack of oil (blocked jet) and too much oil (blocked scavenge). Both are critical. The blocked jet scenario will lead to a bearing failure so fast you probably won't see anything abnormal. The bearings will come apart or melt to the point that the pieces are too big to fit down the scavenge to get to the chip detector. The blocked scavenge will flood the space and lead to the explosive failure as described by NL. The #8 bearing is capable of the same. In the case of a pure leak (i.e. mechanical) in this area you will actually lose air from the engine and end up with high TOT and loss of performance the oil will not leak out when the engine is running, it will with a blocked scavenge though or in the previous case on shutdown.

Regarding the "lower oil temp with less oil". This is still the case as the mass to be cooled is reduced. The "example" of the 206 gearbox is that it is a very simple system which has thermostatic control and can reach temperature limits even without the quoted "foaming". Why does more oil leave the gearbox once it is aerated? Because it takes time to de-aerate - simple.
The problem is the delta T to be achieved. For instance if the cooler was 100% efficient it cannot lower the temperature below the cooling medium which in this case is air. The thermovalve complicates the issue slightly as it is trying to increase the oil temperature, when it reaches its limit you are then stuck with the difference achievable in temperature as described up to the limits of the oil. For example if you increase the size of the cooler or reduce the amount of oil (mass) the result is the same. Look at it this way, you have 2 buckets of water, one hot, one cold, the cold one in this case is the cooler and it's size is fixed. The hot one is the transmission oil which has a heater in it and we are making it larger or smaller. What happens when we mix the two together and look at the resultant temperature? Heat energy in its pure form cannot be made or destroyed just moved - First Law of Thermodynamics. The rate through the cooler is constant and with more oil in the transmission it stays there longer to absorb more heat.

That's the way I see it - End modified rant.

PPRUNE FAN#1
12th Jun 2003, 23:24
Ascend Charlie asked:Nick - I wonder why this sort of info isn't readily available??

I have been flying turbines for 34 years now, and this thread is the first time i have ever seen this information. A bit scary that "shutting down" the engine will have no effect and it will burst its breeches with a cloud of dust and a hearty "hi-ho Silver".

It should be taught in any turbine ground school. I have done the Allison school a couple of times and they didn't talk about a major internal leak at all.That's because:
A) It's not a problem to worry about; and
B) It doesn't happen.

Well, I take that back - we've all seen some massive internal oil leaks caused by bearing or seal failures. Happy Landing ! can attest to that. But Nick's theory is that an engine could develop an oil leak so bad that the flow of oil could exceed that of the fuel...and that the engine would happily run exclusively on that oil while the FC took a break and ran itself back to idle.

Umm... Well, maybe...if we had a humongous oil supply.

The RR/Allison 250-C20B in my aircraft consumes about 25 gallons of fuel per hour in cruise. This means that a tad over 1.6 quarts of fuel are being slurped every minute. If the engine should "suddenly" switch over and start using oil instead of fuel, how long do we think it would run before exhausting the oil supply? I'd be completely out of oil in under four minutes. How much oil does *your* system hold?

Trouble is, we wouldn't even be starting from 100% full, even if the tank was filled to the very tippy-top prior to take-off. Oil leaks *generally* develop over time; they don't immediately go from "no leak" to "full leak" although anything is possible. But for argument's sake, we'd have to assume that before the engine began consuming all oil and no fuel, the oil supply would have to have been drawn down somewhat. And once all of the oil was consumed, the engine would revert to running on fuel, albeit for a very short time.

I'm not disagreeing with Nick; his scenario is certainly plausible given the design of turbine engine FCU's and governors, and it's neat to speculate about such things from a theoretical aspect. It's just not something that we, as pilots, really need to dwell upon in a practical sense. Because if you develop such a massive internal oil leak as he described, there is no alternative: the engine is going to go BANG! very shortly for one reason or another.

(Oh, by the by, we keep talking about "seeing reduced oil pressure" as the oil runs out. Remember that in flight, the first thing you'll probably notice is that the torque gauge goes bonkers, as it is powered by oil pressure in the 206. On the ground, at idle it would be normal to see reduced oil pressure.)

Bladestrike
13th Jun 2003, 04:36
I'd agree with that. My oil pressure went first on the above incident, but on another incident on a 206 where an oil line was not retightened properly following maintenance, it was the torque gauge that went bonkers (extremely erratic) long before the oil pressure started to drop, which it eventually did (over a bunch of trees again). I had an engine let go in a 206 following an engine overhaul as well, and it was the torque gauge that went erratic first, followed by the ol pressure, followed by a chip light, but I was on the ground by that time.

James Roc
13th Jun 2003, 07:38
Hey Happy,

Glad you made it safely to the ground. Have you still got the Raven II? Mine's flying like a dream and I'm up in it most days weather permitting. Changed the governor as you pointed out and no problems so far. I'll be flying her back to Denham shortly for the 50hr and for re-tracking as it would have bedded down sufficiently by now. Maybe we'll meet up and if so it would be nice to fly each others machines for comparison.

Talk soon...James

vorticey
13th Jun 2003, 21:14
im verry interested in your theory about less oil being cooler, you said; Heat energy in its pure form cannot be made or destroyed just moved - First Law of Thermodynamics.
so if the gearbox heats 1 litre of oil 10deg in one min, then the cooler must be capable of cooling that litre 10deg in one minute aswell. if i put another litre in the gearbox the temperature will only rise at 5deg in one minute but the cooler will still cool one litre of oil 10deg. in that time. (no difference)
you also said > The rate through the cooler is constant and with more oil in the transmission it stays there longer to absorb more heat.
but heat rise in MORE oil would be slower! oil stays cleaner longer aswell (impuritys that are suspended are more dispursed) i think reserved oil could only be a good thing.



:ok:

paco
13th Jun 2003, 22:40
I seem to remember something in the flight manual of the PA 31 that said something about watching for increased oil temperature if the pressure gauge fails. I don't think it's a fallacy that the oil gets hotter if it has to work harder - it seems to depend on the positioning of the temperature probes and how much oil is going over them.

Phil

Happy Landing !
14th Jun 2003, 05:48
Thanks Jim,

Call when your next over, will take you up on on the offer, With a drop of the Black Stuff to finish the day !

Fly Safely

Happy !
:D

WLM
16th Jun 2003, 17:03
Hi there
I am looking for some software that will calculate the W & B for a B206 III. I came across it about 18 months ago, written by a pilot in Excel, quite good, but have lost it.
Thanks ;)

EESDL
16th Jun 2003, 18:24
Have a look at the helicopter planning page of B206 CofG (http://www.robertsaviation.flyer.co.uk)
If that's the sort of thing that you're looking for then I'll e-mail a copy!

I'll swap it for a good logbook spreadsheet that does flt duty reports!!

paco
16th Jun 2003, 22:35
There is one at www.electrocution.com/aviation.htm (just scroll down a bit), together with many others. It takes into account the changing C of G of the fuel system. There's also a duty hours spreadsheet, albeit Canadian, but you can adjust it for other purposes.

cheers

phil

GLSNightPilot
17th Jun 2003, 07:14
I wrote one ages ago, in C for DOS, but I'm not sure exactly where it is. I am sure there are better ones available, so I'm not even going to look for it. :D

WLM
17th Jun 2003, 18:02
:O
Thank you for the replies.
Regards
WML :ok:

engineoff
19th Jun 2003, 02:57
With the Ascot time here once again, I was reminded of the arrival last year of a B206 with the pilot flying solo from the left hand seat. I believe the aircraft had just completed a dual flight somewhere and then positioned in.. At the time there was a bit of a debate of the legality of this... Not having a flight manual in front of me I cant say for sure if there is a restriction, however there were some very experienced people on site claiming it was perfectly legitimate.... Could this relate to the age of the aircraft? Have had this before with flying the H500 from the left and then the early military version OH6 from the right.

Surely if there were to be an accident, questions would be asked?? Certainly precludes even attempting an air restart, and makes shutting the engine down when the engine catches fire even more exciting than it would normally be....

Aesir
19th Jun 2003, 07:44
I´m 99.9% sure that the B-206L1 POH states that "minimum crew is one pilot and the aircraft shall be flown from the R/H seat"!!!

Don´t have the manual with me though.

And I´m 100% sure that the B-222 I fly say´s that the helicopter shall be flown from the R/H cockpit seat.

However I have also heard that the B-206 is often flown from the left seat particularly for sling work. There may possibly be a way to do it legally.

EESDL
19th Jun 2003, 18:27
Must have had some form of dispensation to be confident of flying in to an event where ramp checking is almost a certainty.

As stated last year - the manual says that the ac should be flown from the RH seat. A quick search should satisfy.

B Sousa
20th Jun 2003, 00:29
Its obvious that it can be flown from either seat. Others are correct in the "Legality" of it based on the manual. If you can see the Pilot flying it that means an air start is impossble because it takes a few thousand feet to get it started and the pilot to quit shaking after the experience.
Some Im sure are STCd for left seat sling work. More common in the Bell 205

Cyclic Hotline
20th Jun 2003, 06:18
You are right Bert, there are a number of operators with STC's permitting operations (primarily for sling work) from the LH side on various machines. In the old days I have even seen field approvals on 337's permitting this.

In order to complete this modification, all applicable controls are moved to the left-side, so that the RH controls can be removed completely to meet contracting requirements (if applicable) that do not allow controls to be installed with pax in the seat.

Then there are the 205/212 guys that operate from either seat, dependent upon the mission.

MaxNg
21st Jun 2003, 05:10
Enginoff

Single pilot on LHS with low fuel load in a A/C with anti clockwise MR direction ( Left skid low) I would think that you would be getting close to it,s lateral C of G limit.

I tought a very lightweght female in a 206 and that was noticeable but I cant get to my POH at present so cant check

:(

Shawn Coyle
24th Jun 2003, 03:58
The reason for the RH seat only limitation was a crash in the early to mid 80s where the LH seat pilot had the cyclic come off in his hand because it was not put in properly. Not sure of the outcome of the incident, but the end result was that Bell said - thou shalt not, as well as changed the design of the cyclic and collective so they could not be installed incorrectly.
Interesting bit of work.
Basically, if you fly it solo from the LH seat and crash, your CofA is invalid, because you broke a limitation...
Now if someone has an STC for a more permanent cyclic and collective installation, that might be another story.

Cyclic Hotline
24th Jun 2003, 14:42
Bell 206's have been flown, legally, from the LH seat for at least 17 years (that I know off) so probably more.

The nice thing about fat pilots inthe LH seat, is they carry an equally large lunch in the RH seat, so no CG problem there.:ok:

I have a good friend who landed his 206 after bimbling around the mountains and had the RH cyclic break off in his hand! Snapped right off at the airframe fitting! :eek:

The STC's are out there for this.

bailybood
3rd Aug 2003, 06:55
Hi,
I was wondering if anyone had any information on the auto pilot used in the 206B's. Price, capabilities, and such. I don't know what brand or manufacture. I just noticed a 206 for sale that had one and was interested.

Also, is the air condition that's a available for the 206B's worth a cr_p? I know the AC in the EC120 drips water on you most of the time. It does keep you cool, or at least more comfortable, but you do get dripped on. Any comments, good bad or otherwise.


thanks.
baily

paco
3rd Aug 2003, 13:04
Don't expect much power available if you fit airconditioning. As for the autopilot, I know Collins made some, but there was a different suffix if Bell fitted the, although it was the same product.

Worked fine in the LongRanger I once flew.

phil

leading edge
4th Aug 2003, 23:26
I believe that there are (were) some autopilots available for the 206B. It was (is) a contractual requirement for night Marine Pilot Transfer work in Western Australia. Jayrow used to have 2 machines fitted with them.

LE

spinningwings
4th Aug 2003, 23:36
As mentioned above ... Collins had a VFR certified autopilot kit for the BH206 series ...also quite some time ago I got to fly an excellent Bh206 Auotpilot from SFENA brilliant bit of gear which allowed (as I remember it!) a hands off hover ...and I think they got IFR certification for it??? (though I wouldn't bet a "gooley" on it).

Dutchbird
5th Aug 2003, 03:36
Baily,

Go have a look at www.bristowtraining.com

The 206B that they use for the instrument rating
course is equiped with a SFENA autopilot.
Contact Paul Quick, he should be able to inform
you with more detailed information.

Regards,

--db--

bailybood
5th Aug 2003, 07:21
Thanks for taking the time to reply.


:)

baily

TIMTS
28th Aug 2003, 05:14
I am coming up on a 135 checkride in a 206B3, and I am just wondering what kind of experience I am in for?
Any hints or tips, especially on the in and outs of the 206 itself.
The regs and the ops manual is not such a big problem, but I am not VERY experienced in the 206 yet...any helpful hints is greatly appreciated

GLSNightPilot
28th Aug 2003, 08:50
I don't think it's possible to say for sure. It depends entirely on the pilot checking you. The 206 is rather benign, as helicopters go, & has plenty of rotor inertia, so autorotations are relatively easy. Just keep forced landing areas in sight, & put the pitch down in the event of a simulated engine failure. You don't have to slam it down, and if there is a runway close by, that would make an excellent landing area.

RW-1
29th Aug 2003, 00:25
Good luck on your ride!

Devil 49
29th Aug 2003, 05:57
If this is a prehire skills evaluation, anything goes. They're checking to see if you're who you claim to be.

If you're a new hire, your check airman will expect performance and maneuvers comparable to your commercial check ride, with emphasis on company procedures. They want to be sure you can do what's expected of you. You'll also do a route check, covering leg and procedures. Expect to go inadvertent and have to recover from an unusual attitude.
If you've had company technique preached to you, fly the ride exactly as instructed. Forms in blue ink? Have a pen with blue ink. If they said approaches are steep and slow, do'em STEEP and S-L-O-W. If they want two turns around a confined area... you get the picture.

C4
29th Aug 2003, 11:24
TIMTS

Best advice for a 135 ride:

1. You are being tested to the practical test standards (PTS) for a commercial helo pilot. So fly as you normally would and a pass is assured (and easy to boot!!).

2. When asked to carry out a manouevre, carry out the exercise as you normally would do it.. DO NOT try and do it as you think the DPE wants to see it....

3. While doing the oral, take your time in answering the questions.. THINK before answering.. Once again DO NOT try and answer it as you think the DPE wants to hear it.... Answer with what you know... If you are not sure of an answer, tell him such.. But tell him you know where to find the answer, and then find it for him...

4. The biggest thing is to relax and have fun with the examiner.. Treat it as a learning experience.. He/she is not out to get you, but to ensure that you are SAFE.... Are You safe????

Best of luck to you...
C4

Expat in the sun
30th Aug 2003, 03:58
Remember you judgement is being tested as well as your pilot skills, the check airman might ask you to do something unsafe such as land in a confined area that is too small or downwind. He would probably not let you complete the maneuver but is testing to see if you spot the danger and show good judgement.

Good luck :ok:

gulliBell
2nd Sep 2003, 16:35
Has anyone on the forum ever put a B206 in the water without the benefit of deployable floats? How much time would one have to make an exit before it sank below the surface, assuming calm sea state? Any suggestions for a recommended ditching technique should the engine or drive train fail?

The Nr Fairy
2nd Sep 2003, 17:43
Read the accident report for G-OPNI (http://www.dft.gov.uk/stellent/groups/dft_avsafety/documents/page/dft_avsafety_500411.hcsp) - it appears the JetRanger without floats doesn't float very long.

Vfrpilotpb
2nd Sep 2003, 18:04
A Pilot friend of mine put one down in the sea between Blackpool and the IOM, sea state calm, and sky was blue, engine went out and heli went down, he had just enough time to undo the seat belt and open the door as the salty stuff went over his head, at which point he still wasn't out of the heli, so it would seem that they float about as well as a housebrick!:ouch:

Helinut
2nd Sep 2003, 18:09
I was amazed when I first read the G-OPNI accident that it floated as long as that. I would suggest that the experience of VFR's mate is much more typical - It would certainly not be safe to rely on a non-float helicopter floating for any significant time

Robbo Jock
2nd Sep 2003, 20:34
VFR,

Was that the incident where a Cessna flying the other way happened to be looking at him when his engine went, saw him hit the water and subsequently dropped him a life raft ? I recall reading that he had an immersion suit on but the zip wasn't quite done up and he reckoned he nearly died due to the cold water coming in through the 1" gap sapping his strength, such that he could hardly climb into the raft. Very, very lucky the Cessna was around. And top notch thinking and flying (and bombing!) by the Cessna pilot.

As for how long the things float, I should imagine it would depend on what doors/vents/windows are open, closed or smashed. But seemingly, not long.

The Nr Fairy
2nd Sep 2003, 23:19
What it doesn't say in the report I linked to is that the pilot had his heavily pregnant wife with him at the time he went in the drink. He was bloody lucky the wreckage floated as long as it did - otherwise they would be two more statistics.

As an aside does anyone know the pilot involved, and whether he's still flying, or has taken up naked jumping through firehoops instead ?

DSR10
2nd Sep 2003, 23:37
Surely there must be a relationship to bouyancy with regard to whats in the fuel tank. So if you run out of fuel and have to ditch
you have a better chance of survival to face a CAA prosecution.
See another thread.

GLSNightPilot
3rd Sep 2003, 02:06
There is a difference between floating and floating upright. Without floats, the helicopter will roll over almost immediately, because the CG is so high. However, it will float at least partially for some time, depending on several factors. The amount of fuel in the tank, and the integrity of the tank, is one factor. They may float for days if the seas are relatively calm and the tank is intact and the fuel cap seals well. But you may as well face the fact that you'll likely have to exit with the aircraft upside down & the cockpit underwater. It's certainly doable, and HUET training should be a big help with this.

Jed A1
3rd Sep 2003, 03:15
G-MHCC certainly went down very quick in the Irish Sea. So I'm told.

Ask M M-S and I'm sure he'll tell you that G-BHXU went down just as quick in The Channel.

Once the machine is inverted, the cabin is flooded, there is not much bouyancy left to keep the machine up.

Vfrpilotpb
3rd Sep 2003, 17:27
Robbo,

Yes indeed the very same!

PR-B

GLSNightPilot
4th Sep 2003, 08:07
Rough seas and breaks in the fuselage structure can certainly cause almost immediate disappearance. Nothing is certain when an aircraft ditches or flies into the water. I certainly didn't mean to imply that any aircraft will always float - some will, some won't, & some will for awhile.

trimpot
4th Sep 2003, 18:57
What planet are you on? It will filp over in a heartbeat and sink like a stone with a lead weight tied to it. If you haven't done HUET then you are already dead. Sorry to be blunt, but these are the facts.

(this is in a calm sea state, if it is rough your chances are much reduced)

cyclic flare
4th Sep 2003, 22:37
VFR

Rumour has it (this being a rumour network) that the very lucky pilot spotted by the fixed wing who was lucky enough to be carrying a life raft was trained to ATPL free of charge to help him over his ordeal.

Gaseous
6th Sep 2003, 01:36
The pilot who crashed into Windermere a couple of winters ago told me that by the time he got the door open, the aircraft was submerged and going down!! - in January too. BRRRRR.

Rick W
6th Sep 2003, 11:27
A good friend of mine put a B206 Jetranger III in the sea between the Sydney Harbour Heads after the engine failed. I believe he rolled it to the right once it was in the water. My friend and his two crew members got out of it, I think one may have got stuck for only a few moments, all were Huet trained. I believe it stayed submerged a few feet under the surface for a few minutes, the sea that day from memory was very calm. Two army barges were passing by and my friend got them to throw him a line which he connected to the skids. I arrived with my boss about half an hour later and watched the police divers bring it to the surface with floatation bags. Apart from some impact damage around the bottom of the boot area and one of the pitch links broken it was in good nick. If we could have gotten a sky hook right then and there and put it on the army barge alot of the damage caused by towing it to the recovery area may have been prevented. The engineers did a great job in rebuilding this Jetranger and it served many more years flying. A great job and quick thinking from my friend I reckon, I hope I would have done as a good as a job as he did.:ok:

Vfrpilotpb
6th Sep 2003, 16:54
Cyclic,

I thought he was there already, but from then on he is now in much greater things!!;)

B Sousa
6th Sep 2003, 20:50
All interesting posts, and most to the same conclusion.....it sinks quickly and more than likely inverted. One thing I havent seen posted here is based on some rules I read somewhere. They mentioned something like "within autorotational distance from land" OR mandatory floats for work out of the above requirement.
As to floats working well, if all else goes well. Gary Manion can take credit for landing a B206 in the Ocean off St Croix last year. www.aircenterhelicopters.com A rather textbook autorotation after an engine failure. Floats worked and the aircraft was in fact towed to shore and is again flying. Time to give the man a hats off for good piloting.
On the no float list we can also say that recently a Pilot?? placed an Enstrom into Hartebeesport dam area of South Africa (pprune post earlier) without floats. Viewed Damage indicates to me of high speed, low level with what we call "inability to judge height above water." That coupled with girlfriend on board indicates, at least to me, of a Testosterone problem. It did not float.

Dr Illitout
8th Sep 2003, 02:40
I am no expert on the subject but this question reminds me of the sketch by Bob Newhart, on the buget airline. He was asked a similar question by one of his "passengers" and he said "Some stay afloat for twenty, thrirty seconds. Others go down like a rock!!!!!".:D :D

Vfrpilotpb
10th Sep 2003, 17:39
Just a little more info on the incident that my friend was involved with, at the point of landing, it was a conventional skids level touch down, the body then fell over to the left bringing the pilots door effectivly to the top of the body, at this point my buddy exited the craft and just slid into the sea and pushed away and sort of swam backwards away from the Heli, the heli continued to roll over and became inverted showing the belly and skids, however he quickly lost sight of it and did not see it sink for the sea state hid it from his sight, so it would seem that time is not on your side if you land in the wet stuff!:ooh:

Ascend Charlie
10th Sep 2003, 19:06
A little correction to Rick W's post - the engine didn't actually fail, it just ran down to idle. A minor point - Allison could say it was still running, but just not putting out any power.

:O

B Sousa
10th Sep 2003, 22:13
"A minor point - Allison could say it was still running, but just not putting out any power."


I like that answer, sounds like one typically taken from an Insurance claim......
I remember years ago while working on the Surplus Program for Law Enforcement ( As you may know many OH-58s were given out.) Anyway through the surplus system We were also allowed to get NEW Military oil that saved us a ton of money. When brought up in a discussion where the Allison Rep was present and the mention of MilSpec oil was used he almost had a heart attack....Thats bad oil etc.... really went bonkers. I came back with "You mean to tell me I have been flying this thing in the Military for years and the Oil they use is no good"......He got real quiet. I just think he was wanting folks to BUY his oil....

kissmysquirrel
7th Oct 2003, 22:19
you start it up with the back tie down still attached?
Is it gearbox or engine damage which is most likely and does the engine have enough power to snap the tie down?

Helinut
7th Oct 2003, 23:44
It will all be in the "good book" from Bell. However, from past (third hand!!) experience, the engineers seemed to do a lot of work on the transmission, T/R system. But engine damage could also be done too, I imagine.

Always check you can see a blade at 3 o'clock, and it shouldn't really happen!!

ferrydude
8th Oct 2003, 00:32
Free Turbine, no different than start up with the rotor brake on

EESDL
8th Oct 2003, 01:30
Not will the 3-9 O'clock rule stop such a mis-hap but it keeps the blades away from the jet pipes during spool up.

the coyote
8th Oct 2003, 02:23
Depending on what Ng you get to, I have heard that if the tie down snaps the sudden acceleration can just about rip the transmission out, or roll the a/c over. I have seen a pic of a 206 (it was in Canada I think) where the whole tail rotor gear box had detached from the boom from it being started while tied down.

Camp Freddie
8th Oct 2003, 03:17
we always start the first engine on the S76A+ with the rotor brake on, and release it at 50%N1, also at shutdown stop the rotor on the rotor brake with one engine running at ground idle before shutting it down.

also we can bring both engines back to ground idle and stop the rotor on the rotor brake, and keep both engines running in certain situations like loading difficult freight on an offshore helideck when you really dont want to be shutting down unless you have to.

obviously you cant do either of these on a Jetbox, but assuming it doesnt break its tie down and you abort the start dont see what damage it can cause as it is a free turbine, am I wrong ?

Gomer Pylot
8th Oct 2003, 08:00
There should be no damage to the engine, but the torque produced could cause damage to the tailboom or the drivetrain back toward the tailrotor. As long as the engine doesn't go above idle, the tiedown should stay intact, but if the rope is badly frayed, or the knot is poorly tied, the blades could suddenly come free, & then the likely result is a turnover, from the sudden torque and the imbalance from the weight on the end of one blade.

Ascend Charlie
8th Oct 2003, 10:11
This is something that almost every jetBox pilot can expect to do at some time, especially if the job involves a scramble start.
But the flight manual says "Ensure blade is turning by 25% N1" and when i looked up to see if it was turning - and it wasn't - I then shut it off from about 30% N1. Engineers confirmed no damage, except to pride.

The other thing you can expect to do is start it with the fuel valve off. Normal light-off, winds up to about 40% and then goes awfully quiet - you can even hear the laughter of the people 50 feet away watching you.:\

PPRUNE FAN#1
8th Oct 2003, 13:30
Lighting a JetRanger off with the MR still tied down should pose no big problems. You'll notice it soon enough. ...Or at least, you *should* notice it. I've known one or two oblivious pilots who got the bloody thing nearly all the way up to idle before they realized something was amiss. If the tiedown rope/strap breaks things can get...um, interesting and you're probably bug*ered. I've heard about 206's torqued completely over onto their side (strong C-20's!). And I actually saw one that *nearly* went over. It lifted its skid a bit, then dropped it back down hard enough to wrinkle skin (the aircraft's, not the pilot's). If nothing else, the remaining strap ends are GOING to cause some damage as they flail around while you're trying to pump the rotor brake as fast as you can.

I know that what I'm saying next will go against the grain, but I never did subscribe to that "put the blade 90 degrees" stuff. For one thing, it persuades you to forget about the main rotor for the time being and focusing completely inside the cockpit during the start. Wrong!

Here's the other reason: The RFM says that the MR must be turning by 25% N1. If you cannot see the blade, how do you know it is turning? New 206 pilots are usually so overwhelmed by the process that they cannot give a quick glance up to check that the blade has started to turn, but after awhile it shouldn't be all that much of a challenge. In the GOM awhile back, I did catch one engine that my "opposite" had been short-cooling. The MR didn't even budge by 30% N1. I turned the rotor backward enough to actually start to take hours *off* the Hobbsmeter, but to no avail; the mechs had to change the turbine. Had I been one to put the blades athwart, I might not have noticed right away.

Oh, and starting with the fuel valve off is no big deal. If you have a C-20B and you're watching closely, you'll see the TOT start to waver a bit just before it signs off. (This should clue you in so that you won't be surprised next time you do it.) If you're quick, simply keep the button depressed with one hand while quickly flipping the valve on with the other. The engine will re-light and you can continue on your merry way. I've never had...um, I mean I'VE NEVER HEARD OF a C-20B "going hot" if you do this, although it's certainly something I watch...I mean IT WOULD CERTAINLY BE something I'd watch for. (A C-30 is trickier. It doesn't give you the little needle fluctuation that the -20 does.)

Starting with the throttle open can be REAL exciting (and expensive). Fortunately I have never performed this particular trick (yet). Check throttle closed! Then check it again. And a third time. Then one final time just before punching the button. And if you can't remember doing it, do it. There is no danger, and despite what some people say, you *cannot* introduce raw fuel into the combustion chamber by doing this as long as everything is working properly.

Do not ask me how I know any of this. I'd have to kill you. But let's just say that I've been flying 206's longer than I care to admit, and have made just about every mistake imagineable...and some that Bell probably hadn't imagined. I did get into advancing blade stall one day...but that's another story.

Av8r
9th Oct 2003, 05:51
"we always start the first engine on the S76A+ with the rotor brake on, and release it at 50%N1, also at shutdown stop the rotor on the rotor brake with one engine running at ground idle before shutting it down."


Just interested as to why you always start with the brake on?

I too have flown the s76a++ for a few years and I always found the shock loading through the system at brake release can’t be doing the drive train any good at all.
(For others, it’s quite a jolt at release, right through the whole airframe…)
I only started by that method in exceptional circumstances.

Is it because you can, or another reason?

I’m sure your engineer’s cringe watching it.
:eek:

Hilico
9th Oct 2003, 07:38
In the early seventies I saw a Queen's Flight Wessex parked on our school field start exactly that way - get the engines running then pop the brake. Since they were rehearsing for bringing Prince Charles in the next week, I assume they thought it was safe practice, on that type at least.

rotorusa
9th Oct 2003, 08:38
On of my coworkers had this happen recently in an L4. He realized the problem at just under 30% and shut it down. Our mechanics switched out the forward short shaft (a K-flex), as a matter of company policy I believe.

BlenderPilot
9th Oct 2003, 08:49
Here's a story,

S76 started with rotor brake on which is normal, BUT with the blades at 45 degree angles, this one had one of the blades right over the exahust of the engines, I started to suspect when the blade started to "swell" rapidly. It finally grew to about 3 times its original thickness.

Steve76
9th Oct 2003, 10:25
The 76 is started with the brake on to preserve the gyros for the instruments etc...

Canada is the only place I have seen this and I don't necessarily agree nor disagree. I do wonder how the rest of the world has survived for so long without all the zany ideas about operating the 76 around here...
It is simply in the OPM so I have to do it. :rolleyes:

It is ugly and disconcerting to look at when you see the slack (backlash) in the intermediate and TR gearbox's, taken up with such force as the engine force is driven into the TR driveshaft.

Gomer Pylot
9th Oct 2003, 14:56
The provision for starting the S76 with the rotor brake engaged is in the flight manual, so it shouldn't be that dangerous or destructive. The part about not starting with a blade over the engine exhausts is in the manual also, & ours are placarded against it. I don't start with the brake engaged as a normal practice, but I sometimes do offshore in gusty wind conditions.

We also do maintenance runs with the brake engaged, so the mechanics can check things in the engine compartment with the cowling open, one engine running at a time. You can't run it with the blades turning & the engine cowling open, so some leak checks, etc have to be done with the brake engaged. You just have to remember not to turn the brake off.

As for the 206, I once started one on an OAS checkride with the fuel valve off. The checkpilot passed me, saying he had seen me reading the checklist, & I reached up & touched the switch, I just didn't turn it on. I was embarrassed, naturally, but I know I wasn't the first to ever have temporary retreating brain stall. :oh:

I like to turn the blade 90 degrees. By the time you check for blades turning at 30%, it should be passing over the front, & it's easy to see it turning. I've also lit one off with the blades tied down, & afterwards always made one last check to make sure the blades were on the side.

teeteringhead
9th Oct 2003, 18:28
Hilico

That was the normal way of starting any of the military twin turbine Wessexes (Wessi?). The port engine could be disengaged from the drive train and it was normal to start that way in "Accessory Drive". Port engine then becomes world's most expensive APU, but can then get hydraulica and electrics etc on line before rotor start (hyds particularly important!). Starboard engine then started with rotor brake on, some torque set, and rotor started. Port engine then coupled into "Main Drive". Very complicated but it all worked ... used to take baby student pilots about 45 mins to start on their first few attempts though.

Back to the original question: I recall when flying Hueys and Kiowas some time ago, a mate (not me, honest) starting a Huey with the tie down still on. Managed to get airborne (I think it just straightened the hook), no damage to engine (T53 L13-B), transmission or blades......However, tie down still attached to stinger, which very soon got tangled with tail rotor which DID cause a problem!!! Pride and Huey damaged, but no people hurt .... and to make it worse, he had a cabload of Journos onboard....

SASless
11th Oct 2003, 23:37
Ascend Charlie....

I beg to differ....any really experienced helicopter pilot would never do what you suggest. At my experience level....they would have to have bullhorns for me to hear them!;)

Heliport
12th Oct 2003, 01:14
Bell resurrects LongRanger line


Production at Forth Worth factory taken out of mothballs, following 14-aircraft order from Offshore Logistics group

Bell has re-opened the production line for the 206L-4 LongRanger IV following a joint 14-aircraft order from companies within the Offshore Logistics (OLOG) group. Bell had mothballed the line at its Fort Worth, Texas, factory in July after taking the decision in early 2002 to concentrate on 407 sales.

Bell says workers from other lines will be used to restart production of the single-engined light helicopter and the first aircraft will be delivered to Lafayette, Louisiana-based OLOG in May next year. OLOG, which includes Air Logistics, is understood to have specified the LongRanger over the 407 for its deal, due to a list price that was 20% lower.

"The LongRanger and the 407 are complementary, with the 407's extra 15-20kt [30-40km/h] not needed on shorter legs," says Alan Moffatt, Bell European marketing director.

The 407 was developed from the LongRanger IV, with a four-blade rotor and a 815shp (605kW) Rolls-Royce 250-C47 derated to 400shp, providing 450kg (1,000lb) extra external load.

The cabin on the 407 is also 178mm (7in) wider than that of the Bell 206 series it had been designed to replace. Bell is understood to have taken the decision to re-open the production line after 10 months after substantial pressure from OLOG for the cheaper helicopter. Bell says there are no logistical problems in restarting production.

Bell says it has five additional customers for the LongRanger from the offshore, VIP and law enforcement sectors. The line is now sold out for 2004 and 2005, says Moffatt. Sales for the 407 are expected to be around "four or five short" of the target of 50 helicopters, already revised down from 1997's high of 140 aircraft.

Bell is also expecting "double digit" demand for the 430 intermediate twin over the next few months to offshore oil transportation companies in West Africa and the Gulf of Mexico serving "long, thin legs", says Moffatt.

Hilico
12th Oct 2003, 04:52
Teeteringhead, come to think of it I wrote a fan letter to Bristows at about the same time in the seventies and they sent me a Wessex checklist (the flip-over type on laminated card). Haven't looked at it in decades (should send it to the Heli Museum in Weston really) but I remember the line 'Rotor Brake Off and Latched - check rotor rpm increasing'.

PPRUNE FAN#1
12th Oct 2003, 06:21
Bell is also expecting "double digit" demand for the 430 intermediate twin over the next few months to offshore oil transportation companies in West Africa and the Gulf of Mexico serving "long, thin legs", says Moffatt.The passengers' legs? Not in any Bell helicopter I'VE ever flown!

Tis funny how people keep thinking that you can build a better mousetrap. Good to see the old girl back in production. Just proves you can't keep a good design down...for long.

John Eacott
12th Oct 2003, 07:31
Wessex & Sea King (Westland version) are both started with rotor brake on, for #1 & 2 engines, r/brake only coming "Off" after second engine start. Interestingly, both check lists have "rotor brake - On, 320psi min" as the first check, pre starting No 2 engine.

S76 can be started with the rotor brake on or off, pilot's option, according to my check lists.

Re the Bell 206 rotor blade position, I prefer not to have them all the way round to 90 degrees, about 20 degrees off fore & aft put them in sight, but shows the tie down to be removed.

Further to the Sea King rotor brake, bear in mind that the brake would also be applied to sequence the blade folding post shut down #1, with #2 in Accessory Drive.

The earlier reference to 'an expensive APU', I had to refuel an S61 in a remote WA location, and asked the refueller if he'd mind us keeping No 1 running, with the rotor brake on, during refuel. "absolutely not, no way, etc etc".

"How about the APU, then?"

"OK, that's fine....." ;) ;)

SASless
12th Oct 2003, 09:45
PF....you must reassess your standards.....ever set an MBB 105 next to a Jetranger and compared the differences in engineering?

B Sousa
13th Oct 2003, 10:07
Good News. The Long ranger is a great aircraft. For utility the L4, for Charter the 407......

Gomer Pylot
13th Oct 2003, 12:34
The 407 is fine as long as the tailboom stays on. We've put sheetmetal repairmen in the field full time to keep up with the cracks. That thing wasn't ready for prime-time.

Avnx EO
14th Oct 2003, 07:00
Ahh.... Let's correct at least one thing.... The 206L-4 production line and tooling all reside at Bell's Mirabel facility (North-west of Montreal, Canada). All Bell's commercial aircraft are built in Canada. I think it's safe to say that L-4s will not be rolling off an assembly line in Fort Worth. (Although Bell is reputed for changing its mind frequently - I think that one's pretty safe.)

I also think that it is somewhat unfair to refer to the production line as "mothballed" and "resurrected". Although the line may have been on a bit of a hiatus (due to inventory I'd suspect), the 'L-4 has never left the ranks of Bell's active products.

Check the website:

http://www.bellhelicopter.com/aircraft/commercial/

(It was not retired, like say the 205, 212, 222, or 230.)

helical
22nd Oct 2003, 13:39
A question all of those guys and gals who are either tallish or long in the body.
We've become the proud owners of a longranger, however some of our pilots are having a real problem getting their head out the door space, while wearing a helmet, when doing sling work. It seems that the normal seat base is to high for them. Has anyone else run into this problem and what have you done to remedy it. Personally I think the boss should just give me all the sling work, as I'm 5'10" so it doesn't bother me.;)

Ascend Charlie
22nd Oct 2003, 20:34
What you complaining about, Helical?? You've gone from a PretendRanger to a Real Ranger, you don't need water methanol to take off, you don't need to worry about the TOT all the time, and you moan about head room? Some people are never satisfied.....
You took the woolly seats out of Bella to get more headroom, and have already worn through the the seat fabric with somebody's big bum.

Give the jobs to the short guy.:sad:

The Nr Fairy
29th Oct 2003, 14:08
Anyone know if such a beast exists in the UK ? And if so where and how much they are (to rent) ?

I want to get a head start on the 206 type rating, and the spectre of hot starts, overtemping, overtorqueing and the subsequent large bills seems to be looming large . . .

Johe02
29th Oct 2003, 18:17
I fly from http://www.heliair.com/

They've got one or two 206's. Pretty sure they can do it. .

BlenderPilot
29th Oct 2003, 18:40
don't worry.

The 206 must be one of the easiest, "foolproof" helicopters there are to operate, few bad habits, predictable, good handling.

Don't worry, just enjoy.

The Nr Fairy
29th Oct 2003, 20:05
While I'm at it, does anyone have a manual for the B206 I could persuade them to part with ?

Hedski
30th Oct 2003, 03:11
If you want quality without trying to be stingy, I'd suggest Alan Mann at Fairoaks. Great course, get Bell factory cert. at end and a nice white manual. They know anything Bell back to front and inside out, thorough and well worth the extra.
Talk to Gary Savage, and enjoy it, turbine rules :ok:
Hedski

EESDL
30th Oct 2003, 17:04
http://www.lsirucker.com
The site has a good 'manual' area you may wish to use

Figure Of Merit
30th Oct 2003, 22:03
Hi

I've got a spare copy of the Pilot Transition Manual from the Bell course that's yours for the post and packing. Also a copy of a POH from the same source that you're welcome to borrow and risk breach of copyright law with.

I can highly recommend the Bell course. If you can find cheap flights (Dallas) then you'll end upo spending pretty much the same in he UK or in the USA. What you'll gain is great professional ground school, tons of auto's and people who can answer just about any question on the machine.

Having said that I've let my 206 rating lapse- never made sense not to take a 44 instead.

PM me if you want the books.

FOM

mattychopper
31st Oct 2003, 09:11
Hey,

I'm short and can wear a cowboy hat on top of the helmet and do just fine....

Just tell me where I need to show up and how much the job pays


:ok:

two0six
10th Nov 2003, 20:36
To all the J.R gurus out there can anybody enlighten me on the following quirky questions?

1. Roughly how many litres or gallons does a 206 burn at idle.

2. Why when Nr is tweaked to bottom of the green in the cruise does TOT marginally decrease then 2 seconds later return to previous cruise temp.

3. Under various Air.Nav.Regs. around the world can you fly doors off with pax (tourists) legaly as POH says its allowed.

Am fairly new to the heli industry and learnt a fair bit from all the ppruners ( Although much of my knowlege gained has been on the pay package you all get! ):D

sycamore
11th Nov 2003, 01:56
206,
1. guessing, but at idle/idle, probably 3-4 gph, at 100%/idle probably 6-7 gph.
2 because , assuming you have maintained speed, and height, the torque /power requirement has remained the same:ie, you have increased the collective and adjusted the yaw pedal by a little bit, so the "guv`nr" says , i now need a bit more fuel to compensate.Works the other way as well.
3 Company OCM will say, unless State CAA override.

overpitched
11th Nov 2003, 05:14
With the fuel I find that during normal ops we burn around 100L/HR. If there is a lot of grond running say 50/50 than that fuel figure goes down to somewhere arond 75-85L/HR

We fly pax with all or some of the doors off. I find the best combination of vis, pax comfort and speed is achieved with front doors on and back doors off.

Fatigue
11th Nov 2003, 09:16
hey two0six, don't know about Q.2,3.. but I looked for you today and at flat pitch, engine idle, fuel flow indicator read 10 (U.S.) gals per hour...:ok:

BlenderPilot
11th Nov 2003, 10:32
I was doing a maintenance acceptance flight today of a 206JRIII (Allison 250-C20) with fuel flow indicator, it gave me the following reading´s

Flat Pitch, Idle, 8%TQ = 7.8Gal/Hr

Flat Pitch, 100%NR, 22%TQ, = 13.6Gal/Hr

In flight, 50%TQ, = 18.3Gal/Hr

In flight, 60%TQ, = 20.5Gal/Hr

In flight, 80%TQ, = 26.3Gal/Hr

In flight, 100%TQ, = 30.7Gal/Hr

All of these were taken between 7,600 and 8,500 FTAMSL so I think readings would be a little higher at SL

Save for reference.

overpitched
11th Nov 2003, 15:31
Blender.....

I'm curious ??


What is a maintenance acceptance flight???

two0six
11th Nov 2003, 18:01
Guys thanks for the replys on the JR !!

two0six.:ok:

BlenderPilot
11th Nov 2003, 22:38
I guess I should have explained myself better.

I work at the main Bell Helicopter Service Center over here, and we get machines from all over that come here for maintenance. Whenever a helicopter first arrives, we fly the aircraft around for a while ourselves to record all parameters, do a power check, check the NR revs in autorotation, and look for anything else unusual. Then before the helicopter leaves we fly it again by ourselves and with the customer to do the same thing.

That is we call a, Maintenace Acceptance Flight.

Happy Landing !
11th Nov 2003, 23:03
What a great idea!

Why don't all service organisations do that?:(

sycamore
12th Nov 2003, 01:46
HL
usually because owners whinge about using hours/fuel etc, without realising that an a/c can come out of the shed after maintenance with a lot of the same snags it had before-- engineers can`t fix things they don`t know about, and everyone carries snags on a day to day basis.Then when a maintenance flight is done and the discrepancies are noted ,it causes further delay . T hats why a pre -maintenance test should be performed; it also standardises everything, if it`s done by a small team.

Ascend Charlie
12th Nov 2003, 05:45
You will also find that most smallish maintenance companies don't have a pilot sitting around to do such flying. Even the big companies rarely have a slave pilot. Sometimes there is a low-time jockey, but aircraft owners don't want a bograt flying their machine, and his experience is likely such that he wouldn't know if a machine had something minor wrong.

Having done some maintenance test flying myself, I can say that it is often brain-numbingly repetitive and boring. I got out of it as quick as I could and into gunships. :p

belly tank
1st Feb 2004, 14:30
hAVE A LOOK AT THIS GUYS, good for us 206 operators!!



Fort Worth, Texas Jan 16, 2004

The Bell 206B3 Jet Ranger is one of Bell Helicopters most successful models with thousands of the reliable aircraft in service throughout the world. In response to customer needs, Bell engineers have recently finished a certification program that increases the internal gross weight limit for the 206B to 3,350lbs, a significant increase of 150 lbs. Take-off at the higher gross weight will require an initial airspeed reduction until a corresponding amount of fuel is consumed.

The increase in useful load will enable the JetRanger to be more competitive in the Light Helicopter market. The additional capacity will benefit the Law Enforcement market in particular, as agencies will be able to expand mission capabilities and aircraft effectiveness. Police units can now carry an extra person or extra equipment without having to reduce fuel load or otherwise limit aircraft takeoff weight. In addition, this useful load enhancement could benefit applications such as power line/pipeline patrol, air tourism and urban forest fighting applications.

The product improvements will be retrofitable to most of the 1,714 Jet Rangers in the field today. There will be a technical bulletin or information letter sent to our customers to introduce the STC, which consists of a flight manual supplement (FMS) and a revised airspeed placard for the crew station.

These performance enhancements represent Bell Helicopters’ continuing commitment to improve its products. Bell takes pride in listening to its customers and working diligently to satisfy their helicopter needs. That pride and commitment will lead Bell forward as it continues to innovate and design quality aircraft .

cheers B. Tank

Aesir
1st Feb 2004, 16:39
Gooo... JetRangers..

No seriously, this is just one more feather in the hat for the JR.

I and my company operate 2ea B-206´s and we are very happy, actually come to think of it have you ever meet a 206 operator who is unhappy :p

Below is a pic taken of us flying our 1970 Agusta Bell 206BII in excellent winter weather today.

Actually for those of you who like to frequent the airline forums! I was taking my friend who owns the airline company AirAtlanta, for a ride.

http://www.helicopter.is/pprune_206.jpg

StevieTerrier
1st Feb 2004, 19:15
An extra 150 lbs payload, eh? And all by inserting an FM supplement and sticking a placard on! What kind of witchcraft is this?

Now, if Bell will supply me with new expanded faces for the TOT and TQ gauges which will allow me to lift this extra weight and still stay in the green, I'll be a happy camper.

Or better still, shoehorn the 407 motor and transmission in. A discreet badge on the bootlid just to signal your intent (PowerRanger maybe or 206BIIIGT?) , perhaps a couple of NACA ducts a-la Lamborghini Countach, subtly flared skid fairings and we're all set.

Hughes500
2nd Feb 2004, 16:05
Who are they kidding, like to see someone get off the ground in zero wind at that weight !

Well I suppose if you wish to play at aeroplanes with a long runway I suppose you would be OK !!

belly tank
2nd Feb 2004, 16:58
AESIR,

That is an awesome pic!!!

what altitude are you at there?......the 70 model 206, just proves they are unbeatable in their class huh, we have a 98 model 206 and its a truly wonderful bird.

the gross weight increase lift it upto the external load limit, however with all these things there are limits and what you do at sea level is quite different to altitude. im sure this weight increase will keep the 206 drivers happy and legal for all the times they have exceeded 1451kg!!

Aesir
2nd Feb 2004, 17:21
Belly Tank, I was at about 2000´ MSL.

To others!

I have often done sling work at the external load gross load limit of 3350 Lbs in the JR.
It can lift that no problem, even out of ground effect.

But then I usually operate close to sea level and usually below ISA temperatures and a little wind always helps. ;)

John Eacott
2nd Feb 2004, 17:22
H500,

Up to ISA +10C, I wouldn't anticipate any problem with handling the increased weight, and getting airborne without exceeding any limits. Sounds a Good Thing, but interesting that it's taken so long to be certified.

Aesir,

Like the photo, almost a summer's day ;)

ppheli
2nd Feb 2004, 19:05
The limitation is apparently 78 knots IAS until you are back down to 3200 pounds gross through fuel burn. That does not sound like a great limitation to me - take more fuel, and fly slower for 51 minutes (150lb = 85L @<hidden> 100L /hr = 51 mins).

Before, those 51 min were not even flyable, so range is increased by 66.3nm (78 knots for 51m), or take more kit (and balance that against reduced range by flying 78 knots instead of 110). So what types of operation are _not_ going to benefit here? Only the guys already up at 3350lb external, or the hot/highs as well? Slower operations (like law enforcement patrol) will like it, tourist buses will not need to refuel so often, pax charters fly further, etc.

Funny that Bell got the STC for this higher internal weight in 1994 (:ooh: yes, 10 years ago.........) and have only now decided to bring it to market. If I was in their position, it would have appeared just prior to the EC120 being released for sale. Nah, I would have released it there and then in 1994 when production figures were starting to slow and the R44 came on stream.

Any hints of authorities other than the FAA showing interest in this, or even Agusta for the Italian made 206s? or do we have a two-level sales market coming up?

206 jock
8th Feb 2004, 23:35
I managed to pick up a cheap, complete and never fitted top and bottom Wire strike kit for a 206: it's been sitting in my garage for a couple years. I'm now getting off my a**e and looking at fitting it. Does anyone have any experience for how long it takes? One reputable shop over here quoted me 120 (yes, one hundred and twenty) hours to fit one. That makes it way more expensive than the kit cost me

Working on the fact 'that can't be right', anyone know a more reasonable figure and anyone got any contacts this side of the pond?

And, does fitting one get you your money back? Or am I better saving it until I buy a more modern one in a couple of years?

SASless
9th Feb 2004, 00:21
Using it one time for real will make it worth whatever price you pay up front...but 120 hours does seem a bit much. No first hand info to provide but will ask around for you.

widgeon
9th Feb 2004, 06:23
BO 105 installation is around 300 hrs but you have to just about rebuild cabin roof as there is no structure there . AS350 factory unit about 140 hrs and the after market Aero Accesories kit around 80 . Dont know much about 206 structure but I can believe 120 hrs , The 105 kit was designed to have minimal deformation after a strike whereas the 350 is desingned to cut the wires but you would probably need to replace much of the structure after a strike . Take the kit apart check out how many sheet metal parts are in it , once used a rule of thumb of about 10 minutes per rivet that came out close.

John Galt
9th Feb 2004, 09:20
Hi,
Can anyone out there tell me if it's possible to modify a Bell Longranger from an L3 to an L4. From what I understand, the L4 has a thicker tail-boom and a reduced main txsm TBO. (max gross 4450 lbs v 4150 lbs)
Thanks. J. Galt

leading edge
9th Feb 2004, 22:42
My company has looked into this. Basically Bell will tell you that it can't be done economically. There are other airframe mods apart from the tail boom so I understand.

LE

sprocket
10th Feb 2004, 04:25
The T/M has a different part number. FWU and driveshafts are different too. .... and expensive.