Flightsim-pilot questions (Merged)

[Patrick_Waugh]

I fly a sim B206, and wondering when you would need to reset the generator, and what that does exactly.

Patrick

[imabell]

it might make it work again if it has stopped. ??:ugh:

[Aesir]

Hi Patrick

Here is what my SA365 manual says:

"The spring loaded 'reset' function allows the generator to be restored after a transient fault"

In effect the switch resets the overvoltage or reverse current relay who disconnects the gen if the voltage exceeds 32v. It probably does the same in the 206.

[Arm out the window]

The generator is basically an electromagnet spinning around in a coil, as I understand it, as opposed to the old permanent magnet doing the same.
To get it working, there first needs to be the right electric current in the electromagnet coil, so if you hand propped a fixed wing with a dead battery, the alternator wouldn't work because there was no electricity to start it off in the first place.
I think with a genny reset (searching the memory banks here) it 'flashes the field', ie provides electricity to the right connections on the unit to get that initial current direction and amount right to kick off the magnetic fields that make the whole thing work as a generator - the idea being, if for some reason it's stopped working, you might be able to kick it off again by setting up the right initial conditions again.
Then if it still doesn't work, it's probably shat itself, to use a technical term!
So (I think) that's why your genny switch has three positions - on, off and reset, rather than just on/off.

[Gomer Pylot]

For what Patrick needs to know, the generator switch goes to the OFF position when a fault knocks it off, just like a circuit breaker. In order to get the generator to work again, you have to move the switch to the Reset position, then to the On position. Just moving it to the Reset, or to the On position, won't restore the generator. You have to move it to both positions, and if the fault was momentary, then the generator will start working again. Depending on the fault, it may still not work.

Edit: As far as I recall, the switch won't actually move to the Off position, you just get a generator light, and then you move the switch through the OFF position to Reset, and then back to ON. The generator may or may not be restored. If a couple of cycles doesn't restore it, then you assume it's out for good, and rely on the battery. You hope for 1/2 hour of battery. The engine will continue to run without the battery, of course, but your avionics and some instruments will die.

[Upland Goose]

Arm out of the Window.
I think you are spot on. I have always believed that it "flashes the field" as well. That is, realigning the polarity of the permanent magnet field windings.
It's possible that this would not be the case if you had previously selected the battery off - due to overtemp perhaps? Discuss.
This polarity may have been disturbed (reversed) or removed due to major fault on electrical system, which precipitated the genny dropping off line.
If you have a real "meltdown at 3 mile island" then heaven help you!
It's times like that you wish you had the simplicity of a Tiger Moth!
UG;)

[Patrick_Waugh]

Thanks guys. I am starting to get it I think.

I read up on alternators, and it seems the main difference between a generator and an alternator is that they create DC current differently.

The generator uses a moving coil in a fixed magnetic field (which is basically an electo magnet powered by the engine).

The alternator uses a moving magnetic field (the rotor) within a fixed tri-coil that allows it to generator AC that feeds a rectifier to convert to low-ripple DC to charge the battery and feed circuits.

Now, both require an initial electrical source to create the magnetic field used to allow it to generator current. So, I am now understanding that the reset allows you to reset the field and attempt to recreate the conditions necessary to restart the generation of electricity.

Seems there is a difference of opinion of if the switch must be manually moved, or will spring back to OFF, and then be manually moved to GEN.

Also, given the superiority of alternators to provide significant current at low engine RPM (idle) why do they still use generators in aircraft?

Finally, if your alternator/generotor fails, and you are now on battery only, and you were unable to land until the battery completely discharges, would you risk a flame out due to a lack of power to fire the ignitors?

Patrick

P.S. You guys are great for helping me.

[Arm out the window]

Units used on aircraft like the Bell 206 are not just generators but starter generators, ie they work as motors initially to spin the compressor for start, and will then come on line to operate as generators once the engine's running. There are various control circuits to make sure they do the appropriate job at the right time, as well as the switch settings called for in the checklist.
I think it must the requirements of this dual role that makes the starter generator the weapon of choice for this type of engine rather than the alternator - obviously easier and lighter to have just one unit, as well.
They do use alternators on light fixed wing, I think. Not sure about the small piston rotaries like the R22?

[fkelly]

The engine wouldn't fail with a flat battery; once it's running it's just a blowtorch with no ignition [let's ignore auto relight etc]. As long as the engine driven fuel pump can suck up the fuel the engine will run. More advanced engines with electronic fuel computers will also run as they have dedicated engine driven generators to power the computer...if they don't they wouldn't be...more advanced..

[Patrick_Waugh]

If you left the generator switch in the ON position, and attempted a start (of a B206 in my case), what would happen when you pushed the starter?

I'm sim'ing this, and wanted to know.

I'm guessing that the generator switch switches between starter mode and generator mode, and so basically nothing would happen. You would hear silence instead of the starter motor.

Also, quick question. Is the gas producer gauge showing N1, and the Power turbin/Rotor gauge showing N2? Just checking my understanding.

Patrick

[rotorfloat]

Your starter would still function as a starter with the gen switch in the on position.

You are correct about the N1, N2/Nr guages.

[NickLappos]

Remember the gen switch is simply a means to ask the GCU (gen control unit) to make the machine turn into a generator. That is why the reset function works as it does, it simply asks the GCU to let the gen come on line.
Similarly, the GCU will not let it generate while it is a starter.

GCU's are clever fellows. Take care though, the Generator will pop on as soon as the starter is switched off, so the engine will see the big generator load, perhaps dragging it down.

[Ifrboy]

Nothing special will happen if you attempt a start with the gen switch switched into the on position.

The only thing that changes is that the generator will come online right after you release that starter button instead of when you manipulate the switch to the on position.

This isnt entirely without danger tho. This on its own isnt that dangerous, but it will cause an extra load on the engine and it might happen that the engine isnt powerfull enough at that speed, causing a drop in speed. This might drag the engine below the minimum self sustain speed, and if not taken care off, will give you a nice pudle of melted turbine parts.

[Patrick_Waugh]

Ok, I am getting it.

So, the main bus, and basically everything in the B206, is powered first by the battery, then by the generator (ie. engine) once the engine is fired up and the generator is switched on (and working).

Is there anything you can't turn on with the engine off? (ie. that requires the generator is powering it)?

Also, can you at least turn on the panel lights (to see what you are doing) with the battery off?

Thanks a bunch guys,

Patrick

[Patrick_Waugh]

In the B206, you have the switch on the overhead that powers the attitude and directional gyros. Is all that is required to spin those gyros up the battery on and that switch on? Or must there be engine power?

I realize that they probably would drain the battery quickly.

Patrick

[Hilico]

From earlier discussions on this topic, there's also the possibility that the quill shaft might snap - the sudden reversal of load from starter driving engine to (now) a generator being turned by engine causing it to fail in torsion.

[Dis-Mystery of Lift]

You cant turn anything on with out the battery on.This is a good thing so idle students cant leave switches on and drain the battery etc(Pays to check whats been played with before flicking Bat on):= .You do have to pop your fuel Boost CB's as one works directly off the battery.Leave it on for a few days and no starty!!Do all night starts with torch in mouth to look at dials(When ground Power not around):ok:

[helilad]

From what I remember of 206 is after start you idle at 60% for 1 min then increase n1 to 70% before engaging gene.I understand the 1 min gave the engine a chance to stabilise[without a gene load] and the reason for increasing to 70% was to avoid dragging n1 down below the min60% n1.

Any takers on this theory?

[tomstheword]

Every switch in the helicopter will work with the battery turned on.

Every switch in the helicopter will work with the battery turned off if the generator is working.

You can always wait until the helicopter is running before turning them on.

[nimbostratus]

You cant turn anything on with out the battery on.This is a good thing so idle students cant leave switches on and drain the battery etc(Pays to check whats been played with before flicking Bat on):= .You do have to pop your fuel Boost CB's as one works directly off the battery.Leave it on for a few days and no starty!!Do all night starts with torch in mouth to look at dials(When ground Power not around):ok:
In my experience it's only the Longranger that has a boost pump that is operational with the battery switched off (could be wrong though!).

[that chinese fella]

The 1 minute time before switching the generator ON is only applicable if the engine has been shut down for more than 15 minutes. See the "Caution" caption of the Start procedure in the AFM.

[Patrick_Waugh]

I need to know what the instrument lighting is like on the B206 to sim it.

Anyone have a pic of the instruments at night to give me an idea?

Patrick

[Jez]

Why not "sim" an AS355N? It is a "staged" shot but doesn't look too bad.

http://i96.photobucket.com/albums/l176/pilot355/819c82b6.jpg

[Brilliant Stuff]

Love the boat. Nice shot.

[Patrick_Waugh]

That is a gorgeous picture. And helps to give me some ideas of the lighting.

I would love to sim the AS365, and perhaps will do one next. First I have to get one done to fund further development. Right now, I'm looking into doing custom instruments for people.

Patrick

[helicopter-redeye]

Can you not just take the one from MS Flight Sim and use that. ?

h-r;)

[Chiplight]

Here's something...

http://www.henry1.com/nvg/407_NVG_panel_0418.jpg

[Patrick_Waugh]

Hmmm this is a 407, but also gives me ideas.

Someone asked why I can't use something for FS. Well, the lighting used in default aircraft is very primative, and is already available in the gauges I have created, but I am using programming tecniques to go beyond their capabilities to add reality.

I guess in the end, it depends on the instruments you have installed, and if they are designed with lighting at all.

Patrick

[John Eacott]

Patrick,

Not the best shots, but these may help you:

http://www.helicopterservice.com.au/photos/pprune/JGE%20panel%201.jpg




http://www.helicopterservice.com.au/photos/pprune/JGE%20panel%202.jpg


http://www.helicopterservice.com.au/photos/pprune/JGT%20panel.jpg

[Patrick_Waugh]

Thanks.

Those do help considerably. It appears that internal light instruments have a light in them near the top that illuminates that instrument.

For the attitude indicator that has no internal light, post lights were added to put crossing mini spots on it.

Thanks again,

Patrick

[Patrick_Waugh]

I have a few questions for someone patient enough to put up with them.

All of the following questions assume an attitude indicator in a helicopter (B206), that is driven by an electric gyro.

1) First, is there always a "pull to cage" knob? I have seen some photos without one I think. I am guessing that if there is not it is because the gyro is incapable of tumbling, and hence does not need it. I would also expect that it would be rare to see one in a helicopter as it rarely would exceed certain bank and pitch limits. If you do cage one, do you need to do this in level flight?

2) If you were to not turn on the gyro during start, but waited till you were in an established constant turn at say 10 degree right bank, and then flipped on the gyro and allowed it to spin up before leveling out, would it then assume that was level, and hence now indicate a bank in the opposite direction?

3) When it is not functional, is there a warning flag? Does the flag say "OFF"? Does it go away right away on power on, or wait until the gyro spins up? When the gyro fails, how long would it take you to notice it spinning down (if the flag were not telling you immediately)?

4) Thanks.

Patrick

http://home.comcast.net/~pwaugh/pics/AttitudeAvitar.gif

[skastdk]

After you spin up the gyro on the ground, you will ned to cage it with the knob! To set it level!

Depending on the gyro system, if you cage it in a turn, it will show a wrong indication when you level out!

You can have different warning flags, but an off flag (orange) could show in top right hand corner!

Some attitude indicators spin at aprox, 18000 to 22000 Rpm, hence it will take a little while for it to slow down! But the flag will show right away!

http://www.faa.gov/library/manuals/aviation/instrument_flying_handbook/

[Avnx EO]

This is probably more detailed than you were looking for .... but here goes....
All mechanical gyros drift over time and require some form of correction. Vertical gyros used for attitude indicators have a biasing mechanism that over time keeps the gyro "dirty side down". That biasing mechanism is based on the assumption that over the long term, the aircraft is straight and level. A lot of times these are mercury switches that apply an small electromagnetic force until the mercury switch centers (gravity down)
So if you were to fly any aircraft in a constant co-ordinated turn long enough, the gyro would eventually re-align and show level flight while in the turn.
So when you start up a gyro, you have to have some form of mechanism to get it where you want quickly, otherwise you'd have to wait for this biasing mechanism to work itself out before you could take off. For mechanical attitude indicators, the common means is to cage (mechanically force) the indicator to straight and level. Other remote gyros had a "fast erect" switch (Viagra for gyros) that dramatically reduced the time required for the biasing mechanism to drive the gyro to the desired position.
Later AHRS (Attitude heading reference systems) perform automatic alignments on power up, so you don't even have to cage or "fast erect." Instead, if the AHRS sees a relatively stable input from its gravity sensors after power up, it automatically performs the equivalent of a "fast erect". Usually when you are talking AHRS though, the sensors are either FOG or MEMs type and you don't really have anything moving anymore. It's all done in math.
That all said, I suppose there might be some mechanical gyros that automatically cage when power is removed. None of the mechanical units I'm aware of, though, seem to have this feature.
Hope that helps you out.

[Avnx EO]

One more thing.... If it's the Bell-installed attitude indicator... the off flag is a red and white striped barber pole.

[Gaseous]

Avnx has done a very thorough job of it. The only thing I can add is that some older gyros use jets of air to bias them. There is a fan on the rotor which is ducted through holes to give air jets. There are pendulums with shutters which partially cover the holes, and when the gyro is erect, all is in equilibrium. The air jets cancel each other out. If the gyro is not erect the pendulums move, the shutters cover some, and uncover the opposing jets, which applies force to the rotor until the equilibrium is re-established. Caging it forces the gyro erect by brute force. I have seen some of this type of instrument with no cage knob but they are pretty old. They are certainly capable of 'tumbling' and you just have to wait until they sort themselves out if they do!!

[Patrick_Waugh]

Thanks. I appreciate all the detail.

Helps to make the sim instrument.

[Patrick_Waugh]

Seems a thing called "thunderstrom lights" is required by the FAA for IFR helicopter operations in the US.

Anyone tell me what those are?

Patrick

http://home.comcast.net/~pwaugh/pics/AttitudeAvitar.gif

[212man]

They are very bright cockpit flood lights, used at night or in poor lighting to bring your eyes' sensitivity to near daylight levels when flying in the viscinity of electrical storms. This prevents you from becoming blinded by nearby lightning flashes, which would be the case if you had allowed your eyes to becoming 'night acclimatised'.

Personally, if the lightning is that close I have my eyes shut anyway......:\

[Patrick_Waugh]

They are very bright cockpit flood lights, used at night or in poor lighting to bring your eyes' sensitivity to near daylight levels when flying in the viscinity of electrical storms. This prevents you from becoming blinded by nearby lightning flashes, which would be the case if you had allowed your eyes to becoming 'night acclimatised'.

Personally, if the lightning is that close I have my eyes shut anyway......:\

Hahahahhhahahaha.

Ok, makes perfect sense. Thanks. Also explains why I couldn't find a thing on them searching google with "aircraft exterior lights".

Patrick

[SASless]

212man is being polite....they are commonly known as "anti-dazzle" lights (UK lingo)....and all the time I thought they were just there to blank out the two big white serving plate orbs shining back at me on the windscreen.

[Devil 49]

The flag may, or may not, drop in the event of a attitude indicator failure. Failures have occurred where the instrument's failure wasn't "flagged". I've seen them "wander" from proper orientation, gradually increasing diversion from proper orientation without a flag. Crosscheck!

[Pandalet]

Wouldn't it be pretty unusual NOT to see one in a helicopter? Any sort of instrument flying (including getting out of a cloud that crept up and pounced on you) would be pretty difficult without an AH...

The gyro seems to wander a lot as it spins up or down (due to the acceleration causing unbalanced forces, I guess), so being able to center it in some way before taking off is rather useful.

[Patrick_Waugh]

I notice that there are some buttons on the cyclic, and wonder what they are typically there to do.

I am guessing that one would be the transmit button, and a hat would be to move a light or camera. Often there is a red button, in addition to a transmit button. Have no clue what that might be.

Patrick

http://home.comcast.net/~pwaugh/pics/AttitudeAvitar.gif

[SASless]

Different aircraft have different setups Patrick.

A stock UH-1 Huey would have five switches on the cyclic grip.

A two stage intercom/radio transmit switch that looks like a trigger on the front side of the grip generally operated by your index finger. A push button switch on the top left edge of the grip for the Force Trim release and operated by your thumb. A push button switch on the left side midway on the grip which had no function, also operated by your thumb. A push button switch at the lower left side front of the grip which operated the external cargo hook release, operated by you Little finger. The last switch was the "coolie hat" which operated the rescue hoist as a backup to the crewman's hoist control in the cabin.

The Huey collective lever had six switches. Engine start trigger under the throttle, engine idle detent switch on top of the collective. Two landing light switches, searchlight switch, a coolie hat for steering the search light, and a Nr RPM control switch. The landing light switch turned the light on and a second switch moved it from pointing straight down to slightly above horizontal, the searchlight switch turned the searchlight on/off and retracted it.

Modern helicopters have an altogether different array of switches.

[Avnx EO]

In most electromechanical instruments, the flag is little more than a confirmation of power.
Actually we've been seeing a lot recently of what Devil has been describing. It's often caused by a resonnance that sets up that sets up on the biasing mechanism (i.e. the mercury starts bouncing around in the switch at exactly the right frequency) and the horizon starts to slowly roll or pitch. It's usually tied to a particular gyro unit and a praticular aircraft configuration (High skids, low skids, FLIR hanging out the front, etc.) And it's usually triggered at a certain speed. We've seen it change with different manufacturing lots on the same model of gyro: You have a model that's worked in the helo for years, then you get a new one and it rolls off. Replace it two or three times and it still rolls off. Swap the gyro into a different aircraft and it works fine. I think part of it has to do with parts obsolescence or changes in manufacture that have come in as the number of electro-mechanical instrument manufacturers dwindles.
Anyway, if you've recently changed out a unit or had some new gear glued to the outside of your helo, or to your instrument panel, watch for it.
Avnx EO

[212man]

Patrick,
I look forward to the questions when you start your S-92 sim project; that should keep us busy for a while!!!:uhoh:

Seriously, a harmless joke and I admire your ingenuity with what you are achieving so far, well done:ok:

[Patrick_Waugh]

SASLess, thanks for the info. It was the force trim release I was forgeting that was driving me crazy.

I am guessing that a "two-stage" intercom/radio transmit switch would work by depressing it to the first point to activate the intercom and fully to activate the radio (or the other way around).

212Man, thanks for your humor and praise. If you like you can always check on the latest at my site: http://picasaweb.google.com/benchmark.avionics where I post public pictures of gauges and the model as I finish them. Right now as I'm working on the instruments, the gauges are what are getting updated everyday.

This project has taken on a life of it's own as I've learned more about a helicopter that I've never flown, or even been in, than I ever imagined. When I was in the Army I was ferried around on and jumped from many of them, but never imagined the fun of flying them. Guess I was having fun just riding on them.

It has been a joy learning so much about them, and one day I hope to actually learn to fly a real one. I do appreciate you all putting up with my unending questions.

As I learn more, the next project will be easier.

Patrick

[Gomer Pylot]

Which buttons are you inquiring about - on the collective or cyclic? The title says one, your question another. :p

As others have said, it depends entirely on the model of helicopter. Bells usually work as you said, pull to the first detent for intercom, to the second for radio. But Sikorsky (at least on the S76) does it differently - push up for intercom, down for radio. This is better, but does take some getting used to after 10,000 hours or so in Bells.

Offshore-equipped models will generally have a float inflation switch on the cyclic, and may have a float arming switch on the collective. They can be almost anywhere in reality.

You really have to learn the layout for each model, and think before you start pushing buttons.

[Patrick_Waugh]

Which buttons are you inquiring about - on the collective or cyclic? The title says one, your question another. :p

As others have said, it depends entirely on the model of helicopter. Bells usually work as you said, pull to the first detent for intercom, to the second for radio. But Sikorsky (at least on the S76) does it differently - push up for intercom, down for radio. This is better, but does take some getting used to after 10,000 hours or so in Bells.

Offshore-equipped models will generally have a float inflation switch on the cyclic, and may have a float arming switch on the collective. They can be almost anywhere in reality.

You really have to learn the layout for each model, and think before you start pushing buttons.

Yeap, I was tired when I posted this the other night. And, I realize they are different. I left it open so I would learn more, and I did.

Patrick

[Project Pilot FH1100]

Patrick, as others have pointed out there are many type of cyclic grips/configurations out there. In a "standard" Bell 206, the little red button on the top of the cyclic grip is *usually* the intercom button. Radio transmit function is handled by the trigger in front.

[John Eacott]

Patrick,

On your website you have two different cyclics on two cockpit shots: maybe you should link what cyclic you intend using, and then someone would be able to give a definitive answer ;)

[Patrick_Waugh]

Patrick,

On your website you have two different cyclics on two cockpit shots: maybe you should link what cyclic you intend using, and then someone would be able to give a definitive answer ;)

John,

Good point. However, without knowing what's strapped on the outside that might be a challenge on the one stick.

I'll likely sim a couple of versions, with functions that can be assigned to different joystick functions as the user requires. I'll likely go with the simpler stick in the base model, and the one on steroids for the versions with tv cameras, flir, or search lights etc., to allow those to be controlled.

Good idea though. If someone wants to take a stab at it, go for it.

Patrick

[topendtorque]

PW
something that's been reported by many media magazines of repute over the years, Stern was one for example, but probably not public knowledges was the configuration of the OZ mustering bell 47's cyclic buttons.

Intercom used be the red one on top like the 206, but was always unreliable so was disused and separate PTT buttons would be located around the cab with a hot mike switch on the console.

In front of the grip was the normal red radio Transmit trigger, and usually two pull toggles mounted on a frame attached to the cyclic below the hand grip, one for Hook release the other for the Siren, which had a mode selector on the siren itself, (six modes and voice select also) which was located behind your feet in front of the seat.

The old unreliable intercom buttom used to be connected to a jigger, the same as an electric cattle prod, arrangement that was used to prod particularly slow cattle via a long probe that stuck out in front from under the chin of the cabin.

Many had tape decks which were tapped into the intercom circuit so's one could listen to your favorite music during the long days.

One dude had his tape deck hot wired to his siren speaker and often played 'Ride of the Valkaries', much to the amusement of assembled horsemen.

[Patrick_Waugh]

With BAT ON, at the beginning of the day, I would expect that the TOT would read below the 1 (minimum mark representing 100 degC) unless you are flying in Hell.

During flight it would read what, about 520 degC?

Then, lets say you land and shut down and come back in 30 minutes. When you turn on the battery, what will it now read?

Basically, I'm trying to sim this, and need some idea of about how fast it will cool off.

How long does it take to cool completely?

Thanks,

Patrick

http://home.comcast.net/~pwaugh/pics/AttitudeAvitar.gif

[Patrick_Waugh]

I'm trying to wrap my head around what torque is in a turbine helicopter.

I get that in a helicopter like the B206, the N1 turbine drives the turbine compressors, and that it's output flow drives N2 turbine without a mechanical connection.

From here I get fuzzy. I am thinking that the N2 turbine drives the rotor via the transmission and mechanical connections.

So, given the above, I get what N1, N2, and Nr are measuring, but not Torque.

Thanks for the help,

Patrick

[Arm out the window]

When cool, it should read ambient temperature (eg 30 or so).
In flight with max continuous power set, about 650 - 690 deg - lower power settings, lower TOT.
On shutdown, down to about 250, then creeping back up to about 350 or so as the cooling airflow goes away.
After 30 minutes shut down, would be back to under 150 easily.

If you want to start up after only a few minutes shut down, cranking the engine without introducing fuel cools it down quickly, so the procedure there is (from temp about 300, say):
1. Crank, watch TOT. It will drop quite quickly and smoothly (say 5 seconds to get below 150)
2. When TOT below 150, 'crack' the throttle and continue start as normal.

[tomstheword]

the gauge itself reads oil pressure in percent of the transmission horsepower limits, But it gets the reading from the engine

[SASless]

Shame he did not ask about "Torque" in helicopter pilots.


















That "torque" occurs when you get up in the morning and head for the Loo....and when you push down on yer willy to wee....your feet fly out from under you.

[R22DRIVER]

Sassy,

You always know how to put a smile on a face!!! :ok:

[Patrick_Waugh]

the gauge itself reads oil pressure in percent of the transmission horsepower limits, But it gets the reading from the engine

Hmmm. The above is greek to me. I guess you are trying to tell me mechanically it is measuring an oil pressure that gives a percent of the trans horsepower available.

So, basically it is the horsepower being used. So, the amount of power required to drive the rotors and other loads on the engine. It shows me what percent of available power being used. How hard the engine is working to do what I am asking.

What then do torques over 100% mean? (besides a new career and a worn engine, haha).

[Arm out the window]

The N2 turbine drives the rotor via direct mechanical links - reduction gearbox to freewheel unit to short shaft to main gear box to mast to rotor.
Torque is a measure of how much twisting force is required at any particular time to keep the rotor turning at the desired rpm (as set by the N2 governor).
Imagine you had to turn the mast by hand - the faster you had to turn it, the more twist force you'd need to put in, and likewise more drag on the rotor (ie more collective pitch), more twist force. In autorotation, airflow turns the rotor, so no torque required from the engine.

As you may already know, torque is how we describe a force acting at some distance from a pivot point - eg tightening a wheel nut when changing a tyre - the same force applied further out on the wheel brace gives you more torque. As a function of both force and distance, torque is measured in units like foot-pounds, or newton-metres.

The connection with oil pressure is that the device used to measure torque on helicopters, called the torquemeter (funnily enough), on many machines uses small axial movements of two meshing gears in the drive train to allow a greater or lesser amount of pressure oil through a valve to a gauge, giving a more or less direct readout of the torque acting in the system.
Therefore instead of giving us a readout in foot-pounds, we get it in pounds per square inch of oil pressure (psi, as per the Bell 205), or just percent, as in the 206.

Percent of what? you may ask - percent of the maximum rated allowable torque that the engineers say we can put through the gearbox. It's just a figure that the designers work out, so you can often exceed 100 percent if the flight manual says you can - eg 105% for 5 seconds, or whatever.

Anything over the flight manual limits is an overtorque, and means an engineering inspection.

[Patrick_Waugh]

Ok, thanks. The turning the tire nuts example let me wrap my brain around it better, and now I better understand the connection to N2 and Nr.

Thanks.

[Phoinix]

Starting engine without introducing fuel only cools down the thermocouples, not the whole engine, so we try to keep that method for really urgent situations only. Or am i wrong? Opening the engine and letting it cool on a light breeze helps reaching those 150° though.

[helipedro]

Opening the engine cawlings it will help to cool down the engine also be aware of readings after cranking the engine. The temp.reading goes down fast while cranking it but after a few seconds it raises again.Its like when you burn a finger. If you blow on it it stops hurting but when you stop it hurts again.:)

[sprocket]

Sí, eso es una buena comparación, helipedro. :D

[Sir HC]

Arm out the window, Great explanation. Good to see that Bachelor of Education wasn't in vain! Bit nippy up there in the hills I imagine! Cheerio.

[rudestuff]

Torque? surely in the US this is called Tork? (cheque = Check, etc...)

[Arm out the window]

Thanks, Sir HC - haven't got to the long white socks and pocket full of pens yet, but.
Not cluey enough to pick who you are either!
Yes, it has been a smidge on the brass monkey side for the last month or so...

[Patrick_Waugh]

What is the small needle (not depicted in the gauge pic) indicating? I drew it, now I have to program it, haha.

http://lh3.google.com/benchmark.avionics/RMPhH3eYABI/AAAAAAAAAyE/12VvVfCzFiM/Gas.Producer.jpg

[chuckolamofola]

I believe you are talking about the 206 N1 gage as mentioned in other threads, if so:

The little needle represents 1% increments of the big needle. Each one of the marks on the big needle is 10% and one turn of the small needle is 10% and thus each mark represnets 1%.

BTW, the picture does not show on my screen...

Regards,


Chuck

[eagle 86]

Many years ago a senior RAAF MTP was discussing N1 obtained during a MTF on a Huey - got "about" 95% - when challenged "surely you could be more accurate - what about the little needle? "What little needle?" came the reply. Taken to Huey by "junior" MTP and little needle pointed out.
GAGS
E86

[Patrick_Waugh]

I believe you are talking about the 206 N1 gage as mentioned in other threads, if so:

The little needle represents 1% increments of the big needle. Each one of the marks on the big needle is 10% and one turn of the small needle is 10% and thus each mark represnets 1%.

BTW, the picture does not show on my screen...

Regards,


Chuck

Chuck,

You probably need to upgrade something to view the latest .jpg format, not sure what though.

Patrick

[SASless]

A generic 206 panel.....

http://img.photobucket.com/albums/v140/Rotorheads/Gallery/intrum1.jpg

[Teefor Gage]

SASless. Any idea how much the manufacturer charges to fit the needles that are missing on your generic panel?
I guess it's a bit like buying a car, unless you check what items will be fitted to the one you are buying you'll get the bog standard one with a wheel at each corner and an engine somewhere under the bodywork......

BTW - chuckolamofola's answer was correct, even thought he was flying blind......

Patrick_Waugh's .jpg doesn't show on my screen either, and I've got all the latest gizmos for seeing wotsits an all........

[Heliport]

Patrick Waugh

Chuck doesn't need to upgrade anything. Your picture link isn't working.

Is this what you were trying to post?

http://img.photobucket.com/albums/v140/Rotorheads/Gallery/Gasproducer.jpg


Two possible reasons:

There's a limit to the length of URLs the PPRuNe software will accept as a links.
I can't remember what it is - it's not reached very often - but you may have found it.
"lh3.google.com/benchmark.avionics/RMPhH3eYABI/AAAAAAAAAyE/12VvVfCzFiM/Gas.Producer"
is a very long link for a little gauge. ;)
I'm not sure Google's picture hosting allows direct links. Many hosting services don't.
Lots of us use Photobucket which does - and it's free.


Heliport

[Gomer Pylot]

Motoring the engine does more than just cool the thermocouples. Air is sent from the compressor through the entire engine, and out the exhaust. It won't cool the engine completely, but it does cool it down as the air goes through. It can take awhile for the metal to cool completely, and a good rule of thumb is 30 minutes, but you can motor the engine until it reads less than 150 and then start it without much danger of overtemping. I've done it probably hundreds of times, and never had a hot start.

[Flyting]

I've been taught to always pop the IGNITOR fuse when you crank the engine for cooling down to below 150 before starting... Is this neccessary or can you simply with-hold the fuel till the TOT drops, and then continue as per normal start proceedures introducing the fuel?

Maybe for safety if there is a chance of fuel still being available to burn in the engine...?

[Patrick_Waugh]

Motoring the engine does more than just cool the thermocouples. Air is sent from the compressor through the entire engine, and out the exhaust. It won't cool the engine completely, but it does cool it down as the air goes through. It can take awhile for the metal to cool completely, and a good rule of thumb is 30 minutes, but you can motor the engine until it reads less than 150 and then start it without much danger of overtemping. I've done it probably hundreds of times, and never had a hot start.

This is SOP according to the Bell manual.

Patrick

[Aesir]

The little gauge has a specific name!!

They used a name for it at Flight Safety DFW for both the 212 & 222 ratings.

Could it have been the "Vernier" gauge or something similiar?

[NickLappos]

Yes, it is a vernier gage. He was a mathmetician who invented a slightly misaligned scale that allowed you to read the last digit to within 10% for any linear scale, so techically the little dial is not a vernier, but it serves that purpose and is so called.

The N1 is a very sensitive parameter. Since the power of the engine is driven by the amount of air the gas producer sends to the burner, and the amount of air is proportional to the square of the N1/Ng, the last few percent do a lot of work for the pilot, and must be shown by a gage that also must show the big swing from idle to max power.

Here is a site that explains verniers.
http://www.upscale.utoronto.ca/PVB/Harrison/Vernier/Vernier.html

[Patrick_Waugh]

Hmm...

Thanks for the info.

The URL for the photo is:

http://lh4.google.com/benchmark.avionics/RMU6W3v_ABI/AAAAAAAAAyM/_t-_TZnksYc/Gas.Producer.jpg

which is kind of long, and perhaps the problem.

Patrick

[Patrick_Waugh]

Why does turning on engine anti-icing in the B206 result in a rise in TOT, and how much does it go up?

Thanks,

Patrick

[eagle 86]

PW,
Anti-ice is bleed air from compressor - to produce same power engine will burn hotter.
For this reason any bleed air service is normally set to OFF when high power settings are required.
GAGS
E86

[krobar]

I see Sasless' jpg has the Rotor and Turbine needles split, or should I just not go there???

[Patrick_Waugh]

I see Sasless' jpg has the Rotor and Turbine needles split, or should I just not go there???

Well with a TOT of zero(0) he's the man at maintaining RRPM.

[Thridle Op Des]

NR is in the green so it's all OK!:eek:

[Project Pilot FH1100]

But the red TOT tattletale light does appear to be on...

[inmate]

Just a little more information. In the 206 series the Anti Ice is normally ON at an OAT of 5 deg C or less in visable moisture (some earlier modles stated 4.4 deg, but I'm not that smart).You will see an increase of aprox 50 deg on the TOT, however should you try to check the function of the anti ice at idle the change is sometimes very minimal and hard to see.
Normally with the Anti Ice on (below 5C) you will not be TOT limited as far as power requirements for a particular operation however, if you are TOT limited then you will be reducing your TOT by 50 deg or, just maybe a power check is in order!
Fly Safe

[Patrick_Waugh]

Very interesting, and makes perfect sense since it bleeds air off.

Funny how when I started this process, all those intruments looked like an overwhelming amount of so much useless data, and now I can actually understand them. The other funny thing too is that now when I try to fly in FS, without my advanced panel I am very aware of the oversimplification.

Given your above info, now I have another question.

I understand that you can be limited by Torque, TOT, or N1. I think I get torque limits. You can only put so much torque on before you start bending things. I also think I get N1(Ng) limits in that at lower preasure altitudes (and higher temps) you will loose power available due to lower preasure and/or oxygen for combustion. And this is why you have a max OGE hover altitude, for example.

I also understand that you can't allow the turbine to get to hot or it melts and the rest of the helicopter may quickly follow. But, under what conditions would "TOT Limits" limit flight ops?

You guys must be amazed that someone that has never laid eyes on a B206 (although I was flown around alot in helos in the Army) has so much interest in one.

Patrick

[Patrick_Waugh]

When cool, it should read ambient temperature (eg 30 or so).
In flight with max continuous power set, about 650 - 690 deg - lower power settings, lower TOT.
On shutdown, down to about 250, then creeping back up to about 350 or so as the cooling airflow goes away.
After 30 minutes shut down, would be back to under 150 easily.


Ok, further research (according to Bell) has indicated that during the 1-minute warm-up (cold start), the B206 TOT should "stabalize" at
520°C, for the warm up at 60%-62% Ng.

Given that, seems that during the 2-minute cool down on landing that it would cool at most to 520°C. So, I'm guessing the 250°C figure you give above is after fuel shutoff, while the turbine is spinning down and still providing some air, but without the heat of combustion. As that dies, then it goes back up. Perhaps at idle during the 2-minute cool down it is a bit hotter. If anyone can observe for me the temp at the start and end of a typical cool-down, would be appreciated.

Also, once the 1-minute warm-up is complete and Ng is raised to 70%, to power up the Generator, what does TOT go to then?

[vorticey]

turbine outlet temperature gauge will read higher on hot days also if the turbine has to work harder like at altitude or if you point the outlet into the wind, this will produce more heat aswell.
hight hot humid is the answer to your question

[Patrick_Waugh]

When you look at the TOT gauge (B206) is the TOT light the little red area at the max 927 degs C, or a larger light like I have on this pic:

http://i91.photobucket.com/albums/k282/Benchmark_Avionics/TOT.jpg