Recognizing Engine Failure

[southernweyr]

I have found that the sudden change in noise and the sudden yaw is the easiest way to recognize a drive failure. If you get into turbulence and find yourself almost lowering the collective because of the sudden changes in yaw then you might be prepared for an engine failure.

[southernweyr]

I have found that the sudden change in noise and the sudden yaw is the easiest way to recognize a drive failure. If you get into turbulence and find yourself almost lowering the collective because of the sudden changes in yaw then you might be prepared for an engine failure.

[betr_thn_Icarus]

Let's redefine "throttle chop". A quick, unannounced roll off of the throttle resulting in excessive yaw and requiring an immediate entry into autorotation.

 

 

That's what I would call it already. A slow roll off is just that and an announced "engine failure" should also be pretty clear. I think if we had been in an r22 it probably wouldn't have happened but in the Bell 47 you have a LOT more time before you have to have the collective down so it is reasonable to chop the throttle.

 

There is so much energy in the blades you can even enter an auto then come to a zero airspeed halt then nose over and regain your speed as well as maintain rotor rpm to continue to your spot. It loses a lot of altitude without much distance at all.

[ADRidge]

Well, I've only had the throttle chopped on hover autos but believe me, if anyone ever chops it on you, you WILL know. When they say "sharp yaw" buddy, you better believe it.

 

On the other hand, I know a guy who had a true engine failure on his crosswind turn at just over 300 feet agl. Very gentle yaw. He said his first indication (it happened in a turn, so the yaw was harder to identify) was the low RPM horn.

 

I guess a pilot should just be ready for anything. Welcome to helicopters.

[rick1128]

My experience has been the opposite.

 

• An alternator diode that failed did not pre-announce itself.
  

• An alternator belt that failed didn't pre-announce itself.
  

• A plastic mechanic's flashlight left in an inaccessible part of the tail rotor driveline did not pre-announce itself.
  

• A misadjusted carburetor linkage did not pre-annouce itself.
  

• Numerous migratory birds that put themselves in the flight path of offshore helicopters didn't pre-announce themselves.
  

• A main pitch link rod end that failed did not pre-announce itself.
  

Among others I've not listed here, I have personal experience with all but the last and first person knowledge of that. Not all failures are engine failures nor are they capable of being detected before hand. If the are capable of being detected before becoming an issue, perhaps the aircraft needs to be grounded until maintenance is performed.

 

Bob

 

Bob, with over 22,000 hours, I have found that MOST emergencies will give some sort of sign they are going to happen. The thing is that you have to see the sign and recognize it for what it is or what it could be. It may not be much notice, but there usually is some sign that something is not right. In the 8 engine failures I have had, 4 gave abnormal indications prior to failure. In the numerous bird strikes (Swallows to vultures) I have had, none were migratory bird. There are charts and notices of migratory birds movements. You just have to know where to find them, the charts and notices, that is. I have lost count of all the electrical, hydraulic, avionics and flight control problems I have had. I know, a misspent youth flying junkers. A majority of the time, they will give some indication of a problem. A pressure and/or temperature that is higher or lower than normal. Other indications that are a little off. A sound that is not normal. Etc.

 

As for your list, here are a few questions/observations:

 

The alternator diode, may have given you a abnormal indication on the ammeter.

The alternator belt, on preflight, was it a little too loose or tight, was there checking or cracks in the belt, were there signs that the belt may have been slipping?

The flashlight did announce itself. The helicopter was just out of maintenance. That is one most dangerous times to operate an aircraft. Brand spanking new or right out of maintenance, you tend to find all sorts of problems. I usually do an extra careful inspection of an aircraft just out of maintenance. I also have a special rule, any tools I find on the aircraft become MINE! I have a really neat collection of Snap On tools and such I never paid for. I have found a ball of metal shavings in a fuel tank. Avionics hooked up totally backwards and so on.

The carb linkage, was the RPM on start higher or lower than normal? Was the RPM change during throttle movement faster or slower than normal?

The pitch link, was the paint broken in a manner that might indicate a crack? Was it mis shaped?

 

As pilots we are not the only ones that can miss the signs of pending problems. I have asked mechanics on numerous occasions about questionable items. And sometimes they even miss. On one occasion, I had an engine temp raising at idle with no reason for the raise. No other aircraft blowing exhaust at us, no OAT rise, no power increase. Maintenance OK'd it. Just prior to takeoff the temp was still increasing toward the red line. We taxied back to the ramp and wrote it up. It turned out the T-wheel was coming apart. It would have been an interesting takeoff. Several years ago, I was flying a Metroliner, I had an engine that the oil pressure was a little lower than normal. On landing while spinning the prop to prevent shaft warping, I could feel it catch. I refused the aircraft, the company turned it over to another pilot who also refused it, when I pointed out the situation. Yes he checked it out also. Maintenance said it was OK and talked a junior pilot to take it. When the EGT, PRM and Torque when crazy, he shut it down. Problem, the number three bearing failed. If maintenance saids it OK and we take it and it fails guess who takes the hit? Maintenance? Guess again. The pilot does.

 

Bob, I am not trying to second guess your experiences, but trying to make a point. I have been an instructor, training pilot and check airman much of my career. And as such have had access to company incident reports and company pilots who will tell all. Out and out engine failures are rare. One flight school I have had dealings with in a five year period, had only one engine failure. It is a busy school using 300C's. That speaks of the reliability of these engines. Turbines are much more reliable. Engine accessories are more problematic. I have had fuel control unit rupture a diafram and start to flood out. Mismatched FCU's, throttle, mixture and carb heat cables break, etc. Yes I have had a few I got absolutely no warning of, but most did give an indication that something wasn't right prior.

[joker]

Good last post from Rick,

 

I agree, many (most) problems will show up in some form or other. Changes in engine sounds or gauge readings are both tell-tales of impending doom. To be able to learn the signs, and to gain experience with these is important, and will prevent many 'surprise' malfunctions.

 

Hence the reason why 'throttle chops' are a good idea - and can be performed safely. It is no good for a student to simply read in a book. The experience must be embedded in his bones.

 

However - there must be a fair share of malfunctions which don't 'self-announce', mustn't there? Of course - if every malfunctioned had adequate warning signs, there wouldn't be malfunctions, now would there?! - Duh?

 

In fact, we (not naming names) recently had an engine failure before TDP during a vertical Cat A Elevated helideck departure at max weight. The crew (over 30000hrs combined) rejected back to the pad. No damage. I have done thousands of these with nothing, yet this reminded us all that it does and can happen - unannounced.

 

Once again, this leads to a need for practical experience. As I said, the reflex must be in your bones and blood - the only way to put it there is by practical repitition.

 

Back to the original question!

 

The poster asks, what to look for. We have discussed this somewhat already. RPM drop, right yaw, nose drop, sound / tone drop, MP drop, lights and tones, etc..etc..

One thing you never get fully in practice is the full compliment of lights and tones. Quite alarming to hear them for the first time.

 

For checkride purposes, watch for the DPE shifting around - putting pencils back in kneeboard, looking all around, looking down at the ground below, left hand getting close to collective, right hand ready to hit the carb heat, feet moving to the pedals, knees ready to steady collective! Those are usually the signs of an impending throttle chop.

 

Remember also, that for both Engine Failure and Tail Drive Failure, the pilot action is essentially the same - reduce power. So a sharp lowering of the collective is not a bad thing. Once RPM / Yaw is under control, you might be able to bring it back in and troubleshoot.

 

Joker

 

P.S. CofG - It's off to Milan for me in September! No more Florida for me!

Edited March 12, 2008 by joker

[relyon]

Bob, with over 22,000 hours, I have found that MOST emergencies will give some sort of sign they are going to happen. ...

You make very good points backed up with your extensive flight and job experience. I hope everyone reading this thread takes note. What you have written is very relavent to keeping people alive and machines intact. However, I think you are making assumptions about me, my background, my education, my experience, and the specific circumstances involved in the examples I wrote about. Aside from my posts here on VR, you have no basis on which to make such assumptions. I apologize if I'm misinterpreting any of your response.

 

I'll not go into my examples more but will point out a couple things. First, unless you have the ability to detect material defects on the molecular level, possess x-ray vision, are clairvoyant, or completely disassemble and reassemble an aircraft as part of your preflight procedure, I assure you that you would not have been able to detect the problems I listed above before they occurred. Second, I didn't list those anomolies I've been able to find on the ground or in the air before they had a chance to become emergency situations - those outnumber actual occurences by a factor of 15:1 or more.

 

Bob

Edited March 13, 2008 by relyon

[C of G]

Squawking 7500...... thread Hijack!!!!

 

 

Joker,

 

Congrats, when do you take delivery? Your OEI from now on should be an easy flyaway, unless they increase the gross again, which I hear is in the works. Best of luck!!!

[Fastlane]

While you're not way off line here, I believe you're giving yourself way too much credit for what you think is possible to know and or do ahead of time.

 

 

How do you "feel" an electronic component or mechanical component is going to fail? Or when a door latch is going to fail and a less than secured item is going to fly into your tail rotor? Or a 16 pound Pelican is going to impact your left front window at 100+ knots? Or ...? While I completely understand the point I believe you are trying to make, you can't possibly know in advance everything that may effect the outcome of a given flight. If you truely can, I think you should be in the business of selling said black magic, or at least crystal balls.

 

Bob

 

Bob, thank you for the well thought out, well put reply. I honestly do believe we're on the same page. I stated earlier, that I was probably out of line, due to my "thin" log book. And, thanks to your reply, and the knowledge of others that have followed, I realized I was indeed out of line. Not so much out of line, but rather "off the mark." I think I'm comparing apples to duck billed platypuses.

Let me clarify my "FEEL," poor choice of words. You can literally "sense" it, not so much feel it. Long time friend of mine once told me that you don't climb into a racecar, you put it on like a pair of pantyhose. THAT'S the "feel" I'm talking about, the one with the machine mystique.

 

Then I read about 16 pound pelicans, door latches, NON-working relays, etc etc. And I thought to myself, "Wow. LOOKIT the dumb kid!" You are absolutely 100% correct. There are other factors out there that come into play. Especially when not in direct contact with pavement.

 

But ya know what? I LEARNED from this thread. And that's why I check the posts here at VR almost every day. Talk about a knowledge base! SHEESH!

 

Thanks for affirming what I DO know, and helping me along with what I DON'T!!!!

 

~Lucky~

[Goldy]

RPM drop, right yaw,

 

Damn foreign ships !!!!!!! Made me laugh when I saw no one questioned it.

 

Goldy

[joker]

QUOTE (joker @ Mar 11 2008, 21:25 ) RPM drop, right yaw,

 

Damn foreign ships !!!!!!! Made me laugh when I saw no one questioned it.

 

Goldy

 

Hmmm. I was wondering if someone would spot that - interesting to see who reads posts carefully.

 

So let's clarify: When an engine failure occurs, the helicopter will instantly yaw to the left as engine torque is removed (counter-clockwise rotating rotor).

 

Joker