Jump to content

Recommended Posts

Looks like it took almost a minute before they figured out to reduce power. The audio for voices is hard to hear. But somewhere around 4:10 you can hear them saying something about "down now" and the power lowers. (It's been a while since I've been in one, but it looks like the power was high)

Link to post
Share on other sites

This seems to play out differently than those low-rpm practice recoveries that we do from time to time. Skip ahead to 3:15.

 

'>https://youtu.be/fe2CN0SIwTk

 

No telling what they were trying to accomplish. Robinson pilots seem to put themselves in all sorts of weird conditions, then blame it on the aircraft. The vibrations start about the same time (3:31) the VSI starts showing a decent rate that reaches a max of 2000 per/min at (3:42). Note the VSI needle at the 3 o’clock position.

 

Screen%20Shot%202016-06-25%20at%2012.16.

Edited by iChris
Link to post
Share on other sites

I generally expect low-rpm when slowing into HOGE for like say a photo shoot, or climbing out of a confined area, or over a mountain, but this guy just seems to be casually flying along, albeit at a rather high MAP, but I guess when your at full throttle, your at full throttle!

 

Robbie pilots do this kind of stuff probably because a lot of them are private owners with no supervision, or boss/company policy to answer to.

Link to post
Share on other sites

 

No telling what they were trying to accomplish. Robinson pilots seem to put themselves in all sorts of weird conditions, then blame it on the aircraft. The vibrations start about the same time (3:31) the VSI starts showing a decent rate that reaches a max of 2000 per/min at (3:42). Note the VSI needle at the 3 o’clock position.

 

Screen%20Shot%202016-06-25%20at%2012.16.

 

 

And he still has power applied, and still has 100knots showing on the airspeed indicator. Looks like no attempt to lower the collective or pull back on the cyclic until well after the horn came on. Made me cringe watching it. Could have certainly unfolded a lot worse.

Edited by superstallion6113
Link to post
Share on other sites

That is one brave instructor.

Know your 'bucket' speed, stay on the positive side, respect power limits and make your option trades before the NR droops. Fly the aircraft, don't let the aircraft fly you. The aircraft flying you is called "an accident".

Edited by Wally
Link to post
Share on other sites

Pretty sure that wasn't an instructional flight, but I'm not sure.

 

Either way, if you keep an eye on the MAP for some time leading up to the decaying RPM, you'll notice that it (the MAP) was all over the place. Some times jumping as much as 5".

 

Once the RPM started decaying, you'll notice that the MAP exceeds 25" more than a few times. Also, if you take a look at their RPM needles, at one point it almost looks like they are pointing down a bit. If memory serves, the needles are horizontal at 80%. That pilot came REALLY close to killing himself and his passengers.

 

I routinely use this video to show my students how poor piloting technique and improper recovery procedures can go bad.

 

Like Wally said, know your limits and don't exceed them.

Link to post
Share on other sites

RTB, I did see a 76-78% RPM there and a MAP of about 27". 95 kts at 2000 ft and the weather, drying mud around that lake...bet the temps were well above 30. He was heavy...you hear him speak of that, trying to fly too fast....not surprised the low rotor happened, but they kept above 23" most of the flight...never slowed down or reduced power. She is not a race car..but sure sounded like someone from Tim T's favorite robbie killin country.

Link to post
Share on other sites

The guy that posted the video was not a pilot. However, he does answer some questions in the comments. It was not an instructional flight.

 

 

I have deliberately left this out because no one knows 'exactly' what happened, its part speculative, and the full story is convoluted. Also chances are by stating what I do know is probably going to lead to more, not less questions. However seeing as you have asked here is what I do know and if it does lead to more Q's so be it. The flight safety team at Robinson have viewed this video in high definition a trillion times, interviewed me (in person at Torrens CA) and have other similar incidents to base a 'most likely scenario', repeat a most likely, not a definite. Here it is..... Pilot has a loaded chopper of 4 adult pax, no luggage, no doors, 1/2 fuel and operating at approx. 1450m density altitude. No weight limits exceeded. Chopper takes off to head south but a strong SE wind creates a bumpy ride. Unhappy with the situation pilot unknowingly overrides the governor by squeezing too hard on the collective. Unexpected wind shear seals the deal by rapidly pushing the cockpit downwards and (here's where it gets speculative) pilot mistakenly lifts the collective to correct the situation, and (if you're a pilot) the rest should make sense. There is one consensus from Robinson however that isn't speculative; the four of us should have met our maker that day but despite making mistakes our pilot kept fighting and did regain control. All comments here about an autorotation are ludicrous, we were never in a position to do one! Pilot may have put us in danger but pilot also saved us, and for that I am eternally grateful, as are my family!

Link to post
Share on other sites

“Unhappy with the situation pilot unknowingly overrides the governor by squeezing too hard on the collective. Unexpected wind shear seals the deal by rapidly pushing the cockpit downwards and (here's where it gets speculative) pilot mistakenly lifts the collective to correct the situation, and (if you're a pilot) the rest should make sense.”

 

How do they know the pilot overrides the governor? Did the pilot state that? Did the governor fail? If it’s considered speculation about the pilot lifting the collective, wouldn’t it be just as speculative to say he overrides the governor?

 

“Pilot may have put us in danger but pilot also saved us, and for that I am eternally grateful, as are my family!”

 

This statement is reminiscent of today’s helicopter industry and to extent, our “everyone gets a trophy” society…… The ultimate question is; would you allow your children fly with him again? If the answer is no, then maybe you should break the chain and save the next family by saying something to someone....

Edited by Spike
  • Like 4
Link to post
Share on other sites

They did say they were at about 1450m DA which is about 4700 feet, so for what its worth there is this:

 

CAUTION

 

Above 4000 feet, throttle correlation and governor are less effective. Therefore, power changes should be slow and smooth.

 

At high power settings above 4000 feet, the throttle is frequently wide open and RPM must be controlled with collective.

That caution goes up to 6000 feet for the Raven II, but I'm guessing they were in a Raven I? Although it is kind of buried towards the back of the POH.
Link to post
Share on other sites

I'm not buying that Robinson story. Maybe it's my lack of faith in what I read on the Internet, but to my untrained eye, what you see on the video speaks for itself. The pilot was in a somewhat steady climb prior to the low RPM incident, then right before the RPM drops, the power goes up. After that, it's just pure luck the pilot didn't stall the rotor. An additional bit of luck is that they weren't much higher. Clearly, the pilot was so confused as to what was going on, that the only thing that saved them was his fear of hitting the trees. The aft cyclic wasn't his recognition of how to fix the problem, it was simply his reactionary pulling back on the cyclic to try and not hit the ground. Which, fortunately, supplied the energy to his rotor system that it had been screaming about for the previous minute straight.

 

I'm glad they made it out ok, buy I wouldn't be thanking the pilot for their amazing skill. Unless, the thanks given is a punch to the throat. And, after they were on the ground, I don't care where it was, I would have walked home.

  • Like 1
Link to post
Share on other sites

I fly robbies at high altitude daily. Power limits are a daily experience. The key to being safe is being smooth, and recognizing limits as they approach. I have had RPM droops, and sometimes even the light and warning horn. I have never seen RPM go below 95%. When you hear that power surge in the engine and hear that RPM change...lower the collective....smoothly.

 

When operating in High, Hot, and Heavy conditions....go slower. Heavy doesnt mean max gross weight either. I have lifted several hundred pounds shy of MGW and still had to be careful due to high DA and calm winds.

 

Four adults and half fuel in a robbie is no light load...coupled with the speed the pilot was trying to fly...and you say it was bumpy?...hmmm something says slower might have been in order...and that pesky collective...

  • Like 2
Link to post
Share on other sites

Not to mention at 100+kts with the MAP well past any yellow range, he is exceeding power limitations nearly the whole time even before the rotor droops. Talk about being heavy handed with the collective...

 

 

Some years ago a low-ish time pilot came to our school in Australia looking for re-training. His license had been suspended due to him being the PIC in a fairly high profile (luckily non-fatal) R44 accident, and the re-training and sign off was a condition to get him reinstated. I was basically supposed to conduct an extended flight review with him, and focus on the probable causes of the accident.

 

For privacy reasons I won't identify the exact accident here, however the state of flight and configuration would have been similar as in the video above.

I had heard about this accident before, and from the ATSB report I already suspected the cause to be simply pilot induced overpitching, as in so many other similar accidents. During the ground portion of the flight review with the accident pilot, it became clear that this person had never actually been taught, and still didn't know, some very fundamental limitations of piston engines.

 

- he didn't know how much manifold pressure you can physically achieve in a naturally aspirated lycoming

 

- ...or what factor altitude plays

 

- he also didn't know what happens once you attempt to exceed this physical limitation, nor had he ever felt the "full throttle" stop on a throttle grip.

 

- he had very little understanding of the reasons behind using a de-rated engine in the R44, or why there is a MAP limitations TABLE rather than just a single number

 

- so unsurprisingly, when initially asked what he thought had happened to him, he gave the standard answer: "I think I had some sort of a partial power loss / engine problem".

 

People naturally don't retain everything they are taught in flight school, but this huge fundamental knowledge gap about a machine in which he had completed the majority of his training and commercial flying afterwards was rather surprising to me, and him.

 

I think a lot of instructors do a really poor job explaining and demonstrating these things. That and the fact that most students have very limited flight time without the use of the governor these days really contribute to this problem.

Edited by lelebebbel
  • Like 2
Link to post
Share on other sites

You can't get any more than the outside air pressure, 29" at sea level. It actually has to be less than that, or else the air won't go into the manifold.

 

So, at altitude, where the pressure drops outside, so does your MAP.

  • Like 1
Link to post
Share on other sites

You can't get any more than the outside air pressure, 29" at sea level. It actually has to be less than that, or else the air won't go into the manifold.

 

So, at altitude, where the pressure drops outside, so does your MAP.

 

Unless the engine has a turbocharger...then 29" is just mid-range :)

Link to post
Share on other sites

Adam, read the question:

 

 

he didn't know how much manifold pressure you can physically achieve in a naturally aspirated lycoming

 

Astro, you wouldn't call it a Flight Manual limit - the power limits in the book are actually a fair bit lower than atmospheric, because there has to be a pressure differential. Higher outside, lower inside, air flows in.

Link to post
Share on other sites
  • 2 months later...

I'm guessing an exhaust valve stuck, that would explain the high MAP and low RPM plus added vibration. Had one happen on climb out before and the MAP spiked and RPM dropped. Fortunately it cleared after only a couple second and RPM came back and things smoothed out...very similar to this video. The pilot was still an idiot for not getting the collective down...bad running engine or not.

Link to post
Share on other sites
  • 2 weeks later...

Hey, we can't all be Chuck Aaron :-/

Link to post
Share on other sites

Perhaps its just the way you are wording this question, but I don't know the answer either?

 

its all in the wording: "the bat cost a dollar more than the ball, the total cost (for bat and ball)

is $1.10, how much does the ball cost?"

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...