Procedure - Stuck Pedal vs. T/R Failure

[Hand_Grenade_Pilot]

In forward flight, the Schweizer 300 series has two different procedures for stuck right pedal [run-on landing] vs. a total tail rotor failure [autorotation w/ the throttle held in the override position].

 

If you look in the General Specs section of the POH, you'll notice that applying right pedal results in negative tail rotor pitch [i believe it becomes negative pitch at about 3/4 travel, but I'll have to verify once I've got the manual on-hand].

 

So here is the thing that's got me stumped; why would Schweizer [or Sikorsky...] recommend an autorotation for no anti-torque but allow a run-on landing w/ negative anti-torque? In my mind, if you could perform a run-on landing w/ stuck right at 0 degrees or negative pitch than you could also perform a run-on with no tail rotor.

 

The only thing I can think of is that it was assumed excessive right pedal [negative T/R pitch] would not be needed under normal conditions and thus you will always have positive T/R pitch in a stuck pedal scenario.

 

Thoughts on the matter are greatly appreciated. I am also curious as to which other air-frames use this same set of procedures.

 

[Astro]

With tail rotor failure, you have no anti-torque capability, hence the autorotation (although I read in a Robbie newsletter once where a guy who lost his tail rotor (completely) did a run-on landing instead of the auto prescribed in the POH (they didn't say why)).

 

With stuck right pedal, you still have some anti-torque there, you just can't change how much, so I guess they figure that some is better than none, and a run-on landing is still better than an auto?

[Hand_Grenade_Pilot]

With tail rotor failure, you have no anti-torque capability, hence the autorotation (although I read in a Robbie newsletter once where a guy who lost his tail rotor (completely) did a run-on landing instead of the auto prescribed in the POH (they didn't say why)).

 

With stuck right pedal, you still have some anti-torque there, you just can't change how much, so I guess they figure that some is better than none, and a run-on landing is still better than an auto?

 

Stuck left/neutral pedal makes sense; the tail rotor is still creating some anti-torque to keep the nose aligned with your ground track.

 

However, with enough right pedal you'll actually have negative pitch, so the aircraft would have an added tendency to yaw right.

 

It seems to me like stuck right & total tail rotor failure should be grouped under the same procedure since stuck right pedal is basically the same (or worse) than having no tail rotor. Unless I'm missing something?

[Astro]

Stuck right pedal doesn't mean that your right pedal is stuck buried to the floor! It simply means that you won't have enough anti-torque thrust to stop a right yaw rate when you attempt to hover (as opposed to stuck left pedal where you'll have too much and thus yaw left), but you should still have some.

 

You may not have enough anti-torque thrust to stop the yaw rate, but it'll probably still be enough to have a slower yaw rate than you would have if you had no tail rotor thrust at all? Yes, you could do an auto with stuck right pedal, but if you're still producing some anti-torque thrust why not fly it all the way down instead?

 

If you want to try a power-on running landing with no tail rotor (like the guy in that Robbie news letter) you'd better have a really good vertical stabalizer! How's the one in the Schweizer?

 

The only way I could see you having negative pitch, would be if you were in a hover and you were making a right pedal turn, when suddenly it sticks? If that were to happen, just chop the throttle and auto down, but I don't see how it could happen in forward flight?

[Hand_Grenade_Pilot]

The only situation I can think of where you'd need to apply a lot right pedal in forward flight is if you were deliberately flying out of trim [aerial photography]. That could put you at negative T/R pitch.

 

But that's an unusual flight condition.

 

I agree with you that under normal conditions, you won't have enough right pedal applied to be at negative T/R pitch. Probably what the manufacturer was thinking too.

 

If you did happen to get stuck at negative T/R pitch, I think it would be a very sketchy landing. I would guess that you'd have to maintain a very fast airspeed [compared to suck left] somewhere slightly above the best rate-of-climb speed. Maybe even set up the landing w/ a left crosswind?

[Astro]

To be honest, I've never actually heard of a tail rotor having negative pitch, so that does throw me a bit! Hopefully someone a little more knowledgeable will chime in?

[ridethisbike]

Depends on your definition of negative pitch... T/R produces thrust to the right to negate the torque produced by the helicopter. At some point in applying right pedal, T/R will produce thrust to the left (right yaw). According to the ASA Test Prep book this is to counteract M/R gearbox drag (M/R during autorotative flight does produce some force on the helicopter causing slight left yaw). I'm trying to think of an example, but am coming up blank. Basically, the friction in the gearbox/swashplate/other bearings makes the helicopter want to spin in the same direction as the rotors. T/R thrust is required to counteract that.

 

 

Anyways, if you just flat out LOSE the T/R, you don't really have much option to perform a run on landing because in order to do a smooth one, you need to apply power. If you apply power with no T/R, the torque produced will create yaw that you can't correct. Which means you're probably going to touch down sideways while still moving. Bad news bears.

 

Having a stuck right pedal, as stated, doesn't mean it's stuck at full travel. You could be flying along, crabbing into a right cross wind and the pedal got stuck. Realistically, it probably won't be a whole lot of right pedal, but it'll be enough to make a normal landing that much more difficult.

[Hand_Grenade_Pilot]

So to sum everything up, I feel like the general consensus is something along these lines:

 

If you encounter a tail rotor failure [in forward flight], autorotating gives the pilot a greater margin for error because, ideally, you are terminating with very little forward speed. At the end of the flare, even if the nose is off-set with your ground track, you shouldn't have enough forward speed to flip the helicopter.

 

A run-on landing is possible, but it would have to be performed at a relatively fast speed. There is a low margin for error because, if the nose if off-set from your ground track, you will most certainly flip.

 

Being stuck at negative T/R pitch won't occur as long as your flying under normal conditions. So it's not really worth factoring in to the stuck pedal procedure.

[Astro]

A run-on landing is possible, but it would have to be performed at a relatively fast speed. There is a low margin for error because, if the nose if off-set from your ground track, you will most certainly flip.

 

The guy I mentioned from the Robbie news letter did it at 40kts in an R-44 (he skidded along for about 130 feet without rolling over), with no tail rotor at all! It also said that the previous week he had practiced running landings for simulated tail rotor failure as part of the New Zealand CAA Annual Competancy Check Ride.

 

So it seems that a running landing is how they do it, as opposed to the auto we are taught to do for "Loss of Tail Rotor Thrust"?

 

I wonder how they handle stuck pedal?

[Rupert]

We rarely, if ever, use full right pedal. (Got a good story about when you really need it.)

 

What we think of as right pedal really means less left pedal.

 

I've seen a lot of different methods for getting a stuck pedal, left or right, on the ground. They all have merit.

 

That said, I particularly like a low power, low rpm, flat approach for a stuck right pedal.

 

Requires manual throttle.

 

Roll the throttle to manual;

reduce power and rpm;

with hand on throttle, point index finger straight down;

shallow approach to ground effect;

slow down;

when below translational lift the nose will tend left or right, depending on how much right pedal you really have or don't have;

point with your index finger in the direction you want the nose to go (index finger left means less throttle and less torque, and the nose will go left; and, index finger right means more throttle and more torque, and the nose will go right).

[ridethisbike]

Being stuck at negative T/R pitch won't occur as long as your flying under normal conditions. So it's not really worth factoring in to the stuck pedal procedure.

 

I don't think I'd go so far as to say that. There's no telling what situation you may find yourself in. If something happens, you'd be better to know how to get to the ground safely.

 

For instance, lets say it's a windy day. You're having to dance on the pedals like a mad man to maintain your heading in a hover. Stuck pedal. What will you do?

 

Or lets say you're having to take off with a pretty strong left cross wind that keeps making the helicopter want to yaw nose left (T/R VRS and vertical stabilizer acting like a sail). Pedal gets stuck during your takeoff roll when you have a bunch of right pedal put in before you roll through ETL and need that left pedal to crab into the wind.

 

These might be extreme examples, but helicopters aren't always flying in ideal conditions with ideal winds.

[SBuzzkill]

With a stuck pedal I'm going to run it on.

[Hand_Grenade_Pilot]

Disclaimer:

I apologize in advance for this brick wall of text that I've just typed.

 

Now, in response to ridethisbike-

 

I don't think I'd go so far as to say that. There's no telling what situation you may find yourself in. If something happens, you'd be better to know how to get to the ground safely.

 

For instance, lets say it's a windy day. You're having to dance on the pedals like a mad man to maintain your heading in a hover. Stuck pedal. What will you do?

 

Or lets say you're having to take off with a pretty strong left cross wind that keeps making the helicopter want to yaw nose left (T/R VRS and vertical stabilizer acting like a sail). Pedal gets stuck during your takeoff roll when you have a bunch of right pedal put in before you roll through ETL and need that left pedal to crab into the wind.

 

These might be extreme examples, but helicopters aren't always flying in ideal conditions with ideal winds.

 

In a hover, you have no choice- you need to initiate a hover auto [assuming the throttle control is on the collective]. In a ship with a fuel control lever [such as the AStar350] I would assume you just reduce collective and set it down.

 

In the second scenario you shouldn't need so much right pedal that you'd be at negative T/R pitch. A little bit of airspeed [even below ETL] goes a long way in reducing the yawing tendency of the helicopter.

 

Continuing onward, in regards to my original post-

 

I was fixated on the fact that negative T/R pitch is mechanically possible. My reasoning was that if a run-on is possible at full stuck right [or near full] & the T/R is at negative pitch [negative anti-torque], then a run-on should also be done with total failure [no anti-torque]. After lots of thought, I am convinced that in powered forward flight there is no situation that would require so much right pedal that you would be at negative T/R pitch [aside from deliberately flying out of trim].

 

(If you're eyes are not yet bleeding, they will be shortly...)

 

So, assuming that you should never be at negative T/R pitch in forward flight, it make sense that there are two separate procedures for stuck pedal and total failure.

 

Why does this make sense?

 

Well, with stuck left you have and hefty amount of anti-torque Using arbitrary numbers [because this all depends on weight of the aircraft, air density, wind velocity/direction] lets say you could maintain directional control and land at 15kts indicated airspeed.

 

With stuck neutral, you have slightly less anti-torque [but you still have some] so you perform a run-on at 25 knots.

 

With stuck right (but not full stuck right) you still have a little anti-torque. You perform a run-on at 35kts.

 

Now... total tail rotor failure. You have no anti-torque. You opt to perform a run-on at 45kts. This is a lot of speed for a run-on landing. Possible? You bet. But there's less margin for error and a higher probability of dynamic rollover if a deviation in yaw occurs prior to touchdown.

 

So instead, you auto rotate. At the end, if the nose may start to rotate a bit [wind, transmission drag, etc] but you shouldn't have enough speed to flip. It's the prettiest option out of two ugly pictures.

 

But you could have negative T/R pitch in forward flight, right?

 

Not under normal conditions.

 

It is my understanding (now) that the design purpose of negative T/R pitch is for the following situations:

 

1.) Flying out of trim to the right in forward flight

2.) Maintaining directional control in a hover with a left crosswind when the T/R is at peak efficiency, before the on-set of T/R Vortex Ring State.

3.) Performing a 0 [or near 0] airspeed turn to the right in an auto-rotation.

4.) Something else I haven't thought of.

 

But, let's say you're flying out of trim to the right on a photo job, you have full right pedal applied, and the darn thing gets stuck? What do you do?

 

Run-on landing? Or an autorotation?

 

In this theoretical situation, I'm leaning towards an autorotation, based on the above logic. I would rather auto rotate then perform a run-on at 55kts [arbitrary number]. But, in a 'normal' stuck right pedal scenario, I would probably perform a run-on [at an arbitrary speed of 35kts]

 

The thing on my mind now; is there an advantage to performing a run-on landing w/ total anti-torque failure instead of performing an autorotation?

 

And Rupert-

Could you please share that story of yours?

 

 

 

 

[Astro]

Its a very windy day. You're dancing on the pedals, when suddenly you lose it to the right! How do you know if it was Loss of Tailrotor Thrust, Stuck Pedal, or LTE?

[ridethisbike]

SBL, you say that now, but there's no way to know what situation you might find yourself in.

[eagle5]

With a stuck right pedal I'll do a low power approach, flare off all my speed, level off, then chop the throttle and set straight down with a hover auto. The best of both worlds!

[ridethisbike]

We rarely, if ever, use full right pedal. (Got a good story about when you really need it.)

 

What we think of as right pedal really means less left pedal.

 

I've seen a lot of different methods for getting a stuck pedal, left or right, on the ground. They all have merit.

 

That said, I particularly like a low power, low rpm, flat approach for a stuck right pedal.

 

Requires manual throttle.

 

Roll the throttle to manual;

reduce power and rpm;

with hand on throttle, point index finger straight down;

shallow approach to ground effect;

slow down;

when below translational lift the nose will tend left or right, depending on how much right pedal you really have or don't have;

point with your index finger in the direction you want the nose to go (index finger left means less throttle and less torque, and the nose will go left; and, index finger right means more throttle and more torque, and the nose will go right).

 

You're absolutely right. But the possibility does still exist to be at full right pedal and it get stuck. That's all I'm saying.

 

 

With that, your index finger trick is friggin genius. I don't think our instructors know that trick out here, I definitely plan on spreading that one around.

[Goldy]

Is it just me, or is a stuck pedal/ TR failure one of the least taught and practiced scenarios?

[ridethisbike]

Is it just me, or is a stuck pedal/ TR failure one of the least taught and practiced scenarios?

 

It's not just you. I'm half way through commercial and all I've done are TR failures (read: instructor jams in right pedal and I have to react.) Granted my commercial training thus far has been focusing on meeting XC and solo reqs. The next half will be nothing but maneuvers and I fully intend on getting every single bit of EP training I possibly can.

[Astro]

OK here's a question. You're coming back to your Class "D" airport, your pedals are stuck. Do you declare an emergency?

[ridethisbike]

OK here's a question. You're coming back to your Class "D" airport, your pedals are stuck. Do you declare an emergency?

 

Yes. Odds are ATC will give me an entire runway or taxiway to land on, and I just may need it. Plus, I probably won't be able to hover back to my ramp in a normal fashion.

 

Hell, if your pedals get stuck you have to report it to the NTSB, don't forget about that part.

 

NTSB 830.5 Immediate Notification

...Notify the nearest National Transportation Safety Board office when:

(a)An aircraft accident or any of the following listed serious incidents occur:

(1)Flight control system malfunction or failure.

[ridethisbike]

Its a very windy day. You're dancing on the pedals, when suddenly you lose it to the right! How do you know if it was Loss of Tailrotor Thrust, Stuck Pedal, or LTE?

 

Eventually LTE will correct itself with some sort of giant input, or when I'm facing into the wind.

Stuck pedal... well it's stuck so I won't be able to move it.

TR failure after a spin or two a pilot might figure it out and EP it to the ground.

 

Those would be my guesses.

[Hand_Grenade_Pilot]

OK here's a question. You're coming back to your Class "D" airport, your pedals are stuck. Do you declare an emergency?

 

Absolutely. Clear the active, have a firetruck & an ambulance waiting. And a spare set of underwear, just in case I botch the landing.

 

The controllability of the aircraft has been compromised. There should be no hesitation or doubt as to whether or not to declare an emergency on this one.

 

 

And I like the finger trick that you posted Rupert- hadn't heard that before.

[Goldy]

OK here's a question. You're coming back to your Class "D" airport, your pedals are stuck. Do you declare an emergency?

 

Always, doesn't matter if it's Class G non towered, or Class B LAX.

[Astro]

Always, doesn't matter if it's Class G non towered, or Class B LAX.

 

To whom am I declaring this emergency at a non-towered airport? 121.5 and to whomever may be listening?, and what will be their response?