Bell 206: JetRanger and LongRanger
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!
My guess was that it was to counter inflow roll, but that's all it was...a guess!
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Papagolf: From some course notes referring to the stabiliser ‘end plates’ ….
..... I presume, as you say, that it stabilises the airflow to assist the vertical fin (which has a 5˝ 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)
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 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)
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......
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......
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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
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
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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..
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..
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bell 206 longranger fuel system
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
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
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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.
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
[ 09 December 2001: Message edited by: sprocket ]
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
[ 09 December 2001: Message edited by: sprocket ]
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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.
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.
Gatvol
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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.
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:-(
Failure in a JR -n problem - 6000' etc
Failure in a LR - lose 10 gals worth of fuel:-(
"Just a pilot"
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.
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.
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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
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
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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.)
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.)
Gatvol
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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
If its below the top of the Range Extender, its time to refuel.........Ha Ha
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206 CG Calculator (Excel)
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
<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
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.
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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>
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>