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HeliTorque :: View topic - Throttle Chops
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HeliTorque Forum Index » Flight Dynamics

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Throttle Chops
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choppedair
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PostPosted: Wed Feb 01, 2006 5:58 am    Post subject: Throttle Chops Reply with quote

I'm sure this topic has probably been beat to death here, but I'm seeking advise so bear with me. I'm training in R22's, a few hours past my private ticket, working on my commercial. My instructor is frequently chopping the throttle on me during flight, over areas where landing spots are few. Reachable, but almost always soft muddy/grassy surfaces surround by trees. Everything I've read (and instinct) tells me this is wrong. I can understand an occasional throttle chop near a suitable landing area but it seems to be getting a bit rediculous...? We practice throttle chops in the pattern, I'm okay with that. But every time we're away from the airport I get chopped. I generally react just fine, and make a power on recovery before getting dangerously low, but it seems like I've read that you should simulate engine failures with a full throttle chop as the engine is more likely to quit. Also, there is no "simulated engine failure" announced. Seems that in the event of a real engine failure, there would be a hell of a lot of confusion because I would think it was him, he would think it was me, whatever. Give me your thoughts!
(sorry if this is posted in the wrong section, mods feel free to move this into the appropriate forum)
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PostPosted: Wed Feb 01, 2006 9:57 am    Post subject: Reply with quote

Robinson Helicopter Company Safety Notice 27, June 1994:

Quote:
Safety Notice SN-27

Issued: Dec 87 Rev: Jun 94

SURPRISE THROTTLE CHOPS CAN BE DEADLY

Many flight instructors do not know how to give a student a simulated power failure safely. They may have learned how to respond to a throttle chop themselves, but they haven't learned how to prepare a student for a simulated power failure or how to handle a situation where the student's reactions are unexpected. The student may freeze on the controls, push the wrong pedal, raise instead of lower the collective, or just do- nothing.-- The instructor must be prepared to handle any unexpected student reaction.

Before giving a simulated power failure, carefully prepare your student and be sure you have flown together enough to establish that critical understanding and communication between instructor and student. Go through the exercise together a number of times until the student's reactions are both correct and predictable. Never truly surprise the student. Tell him you are going to give him a simulated power failure a few minutes before, and when you roll off the throttle, loudly announce "power failure". The manifold pressure should be less than 21 inches and the throttle should be rolled off smoothly, never "chopped". Follow through on all controls and tighten the muscles in your right leg to prevent the student from pushing the wrong pedal if he becomes confused. And always assume that vou will be required to complete the autorotation entry yourself. Never wait to see what the student does. Plan to initiate the recovery within one second, regardless of the student's reaction.

There have been instances when the engine has quit during simulated engine failures. As a precaution, always perform the simulated engine failure within glide distance of a smooth open area where you are certain you could complete a safe touch-down autorotation should it become necessary. Also, never practice simulated power failures until the engine is thoroughly warmed up. Wait until you have been flying for at least 15 to 20 minutes.


For what it's worth, I think the risk involved in suddenly chopping the throttle, far outweighs the benefit.

Go and read accident report after accident report - there is little, if any sign, of a sudden total engine failure (although you'll find plenty of neglected carb heats reports!). You may also find reports of accidents as a result of throttle chops, where the recovery has been less than ideal, and the result is a bent helicopter.

The derated engines on the Robinson aircraft exhibit a high degree of reliability - of course, no-one can be 100% certain that it's not going to fail, afterall it's why we train emergency procedures. But in order to protect the machines, I think one has to be sensible about what is taught.
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aviatorjames
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PostPosted: Wed Feb 01, 2006 5:24 pm    Post subject: Reply with quote

ChoppedAir,

Your instincts are correct!! ..and James Lowe gives one of many good references to the inherent dangers of frequent, unannounced throttle chops.

You have already demonstrated to the instructor that you interpret and respond to the "engine failure" correctly. Beyond that, he is simply putting you and himself at risk.

Tell him exactly what you've stated here about the increased risks of his throttle chops. (There are plenty of instructors around)

Your concern is real, your instincts are correct, and as a CFI and a professional pilot myself, I can tell that you have developed a safety-attitude (self-preservation!) that will keep you out of trouble. If the same instructor encouraged that safety attitude, then he has taught you something much more important than how to deal with just one of a million things that can (and do) go wrong with these machines we fly!!

By what I've read here, I would rather fly with you than with your instructor.

FLY SAFELY !!!!!
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PostPosted: Wed Feb 01, 2006 5:48 pm    Post subject: Reply with quote

Hi,

What poor airmanship, when an Instructor does not brief his student.

Throttle chops are for inadequate Instructors and serve no purpose. (see flight manuals for most light helicopters)

Practising forced landings is of great benefit to a student but throttle chops are suicidal.

Don't do this, but imagine you chop his throttle without warning, the chances are that you will both die.

Change to a more professional Instructor.

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rotordog
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PostPosted: Fri Mar 31, 2006 2:59 am    Post subject: throttle chops Reply with quote

choppedair,

I just got back from the Robinson safety course and the subject was discussed quite a bit.
There should never be a "throttle chop" given but should always be a smooth roll off of throttle. It is also the responsibility of the instructor to ALWAYS make sure there is suitable emergency landing areas available before giving a simulated power fail situation to a student. If for any reason the engine did fail, there would be plenty of safe landing area.

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PostPosted: Fri Mar 31, 2006 4:42 pm    Post subject: Reply with quote

There should be no requirement for a throttle chop. It is actaually quite rare for an engine to stop dead ( other than running out of fuel - no excuse there ) the donkey will normally give you an indication it is not happy - usually yawing left and right as it misbehaves. Even then the engine maybe pulling some power.
You only need to enter autorotation when the ac snaps off to the left ( US heli types ).
I personally roll the throttle back and forwrards to get the students attention and then smoothly roll off. I am trying to replicate an engine failute that I had with the exact same symptoms
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PostPosted: Fri Mar 31, 2006 7:45 pm    Post subject: Reply with quote

Hughes500 wrote:
other than running out of fuel


Even then, I would guess that you get a bit of coughing and spluttering before it finally quits?
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PostPosted: Fri Mar 31, 2006 8:32 pm    Post subject: Reply with quote

"A petrol engine will generally run faster prior to quitting on expiration of petrol distillate"

Quote from 1927 - "The Atco Book of Lawnmower Troubles"

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PostPosted: Fri Mar 31, 2006 8:44 pm    Post subject: Reply with quote

.

Last edited by weekend warrior on Wed Jun 07, 2006 9:31 pm; edited 1 time in total
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PostPosted: Sat Apr 01, 2006 9:52 am    Post subject: Reply with quote

It's a related publication, as we all know that Robinson make hedge trimmers....
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PostPosted: Fri May 05, 2006 8:07 pm    Post subject: Reply with quote

An ignition failure WILL cause the engine to immediatly stop.

Had this happen, while taxiing. I was on the ground, with the blades stopped, and my wife asks, 'why are we stopping here?'.

A guy runs out of the FBO we were in frt of and swears he saw the belts fly off of the 300 I was in.

Really made me apreciate the aggravation my instructors put me through.

By the way, it was a faulty switch.
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PostPosted: Fri Feb 22, 2008 4:54 pm    Post subject: Reply with quote

More students and pilot instructors have been injured or killed practicing 'simulated" failures that become real!

Find another instructor. Although the instructor is by regulation the Pilot in Command, no one is in command of your safety but YOU.
I am also an instructor for fixed wing with almost 30 years experience, and we stopped many moons ago pulling mixtures to shut an engine down in practice for the same reason.

When I trained in RH, my instructor would simply say "You just had an engine failure, or power loss". He expected me to act accordingly.
It is not the "realness" of the failure that counts, only the pilot's reaction to it.

Fly safe.

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