To crash or not to crash...

[Head in the clouds]

I don't know whether these have been seen on this forum before but they're absolute classics so just in case they haven't been posted before....

 

In the first the lady pilot just got away with it, and by all accounts it wasn't very hot or high but certainly looks like heavy was the culprit.

 

In the second the 'senior' gentleman pilot didn't get away with it and the footage of the crash taken by one of the pax from inside the aircraft is ...well... something else. Everyone survived the crash into trees by good luck and a strong airframe. This one was hot, high and heavy, a return from a trip high in the Rockies and has been discussed at length on other fora and it's interesting that it took ages for anyone to twig just what the pilot did wrong. The plane should have flown away from the situation relatively easily except for one thing... BTW scroll down the news report page to find the video embedded in the page.

 

http://dl.dropbox.com/u/11778598/The%20Dream%20of%20D.%20Meyer%20-%20Meyer%20takes%20off!!!.wmv

 

http://news.yahoo.com/blogs/sideshow/video-plane-crash-cockpit-wilderness-idaho-195341487.html

 

 

[Guest Maj Millard]

The first looks like a clipped wing Stintson 108 Voyager. They are not that great at getting off the ground anyway, especially loaded, so why you would want to clip-wing one is beyond me !....She came about as close as you can, and still get away with it !....I suspect she forgot to select take-off flap, as there is none deployed as she goes past..........................................................Maj...

 

 

[RetiredRacer]

I remember reading a report by the lady in the Stintson in a forum a couple of years ago. I can't remember the details now but it was something like the guy at this field just serviced her a/c for her as he had done for years. She had never had any trouble getting out of there before but this time the motor was down in power and by time she realised there was something not right, it was too late to abort.

 

 

[Head in the clouds]

....I suspect she forgot to select take-off flap, as there is none deployed as she goes past..........................................................Maj...

Yeah, I noted that when I first saw it but also wasn't sure what aircraft type it was, hadn't considered the clipped wing thing, and so I wondered whether it actually had flaps...?

 

 

[Guest Howard Hughes]

The first looks like a clipped wing Stintson 108 Voyager. They are not that great at getting off the ground anyway, especially loaded, so why you would want to clip-wing one is beyond me !

You clip the wings to fit between the trees at the end of the strip!

Gotta agree though, the wing to fuselage ratio just looks all wrong!

 

 

[sfGnome]

This one was hot, high and heavy, a return from a trip high in the Rockies and has been discussed at length on other fora and it's interesting that it took ages for anyone to twig just what the pilot did wrong.

Ok, so what did the pilot do wrong - apart from not put it down on all that open land when it was obvious that it wasn't climbing?

 

 

[Guest Maj Millard]

sf Gnome, What he did wrong was not to allow for the high density altitude that day, for that takeoff., which is the effective altitude, plus any other factors such as air temp etc. Density altitude in a nutshell means much thinner air than you would get, if you were at sea level.

 

Maybe this guy could have taken off from this same strip just fine on other days. He could have had a lighter load and the temps may have been cooler, even though the surface altitude was the same, and doesn't change.

 

Density altitude is a triple edged sword. You engine produces less power because the air is thinner (richer mixture), the prop doesn't produce as much thrust for the same RPMs, and the wing won't creat the same lift unless you go faster and carry a higher angle of attack. Juggling the whole three while wondering what the hell is going on, is usually what gets people in this scenero.........................................................Maj...

 

 

[Head in the clouds]

Ok, so what did the pilot do wrong - apart from not put it down on all that open land when it was obvious that it wasn't climbing?

We'll let folks have just a bit more time to think about it, and it's a very interesting one.

 

A couple of hints - the pilot had all his settings just as you would normally do but he was hot, high and heavy so he shouldn't have those settings like that.

 

Second hint, Maj actually mentioned what he did wrong, and assumed it was right too, but it wasn't...

 

This situation is a very easy trap to fall into, I've done it myself several times (slaps head) and it wasn't until we analysed everything about this, on another forum, that many of us realised what we'd been doing wrong when we took off from a high density altitude strip.

 

 

[Deskpilot]

Yeah, I noted that when I first saw it but also wasn't sure what aircraft type it was, hadn't considered the clipped wing thing, and so I wondered whether it actually had flaps...?

Stop motion clearly shows flaps or flaperons ( can't see division line) are not deployed.

 

 

[Gentreau]

Regarding the second video my question would be, did he take off with mixture fully rich as you would normally do at sea level and as is probably written in the checklist ?

 

If so then he should have leaned the mixture to match the thin air, if he had realised that and adjusted it, he would have climbed out better.

 

.

 

 

[Sapphire]

The procedure in taking off at high density altitude is to use some mixture control leaning. You still want the engine to run rich but not so rich that you are climbing out with very low power. As you gain altitude, your power drops off even more. He probably was afraid to lean thinking he would damage his engine, so he let the plane crash into the trees-good choice

 

 

[Head in the clouds]

Regarding the second video my question would be, did he take off with mixture fully rich as you would normally do at sea level and as is probably written in the checklist ?If so then he should have leaned the mixture to match the thin air, if he had realised that and adjusted it, he would have climbed out better.

 

.

 

The procedure in taking off at high density altitude is to use some mixture control leaning. You still want the engine to run rich but not so rich that you are climbing out with very low power. As you gain altitude, your power drops off even more. He probably was afraid to lean thinking he would damage his engine, so he let the plane crash into the trees-good choice

Yes folks you are right. Most people always use full rich for the take-off but the density altitude on the time/day of this crash was, IIRC, about 8oooft, so even for a rich climb he should have had the mixture about the same as for cruise at around 5-6000ft. If you freeze frame the video you get a couple of glimpses of the mixture control pushed fully in = full rich.

 

If anyone has a variable mixture plane try going to full rich at 8000ft on an STP day and see what climb you get at MTOW...

 

And our sad pilot was climbing into rising terrain...

 

 

[Gentreau]

Having never flown anything with a mixture control, perhaps someone can enlighten me.

 

Would you be able to set the mixture at the time of the run-up checks ?

 

I'm imagining setting the normal run-up rpm and then adjustng the mixture to get max rpm ...... ??

 

 

[Head in the clouds]

Having never flown anything with a mixture control, perhaps someone can enlighten me.Would you be able to set the mixture at the time of the run-up checks ?

I'm imagining setting the normal run-up rpm and then adjustng the mixture to get max rpm ...... ??

Yes, it's a bit hit and miss depending on what instrumentation you have and any quirks your plane/engine may have, so familiarity helps.

 

An EGT is almost essential to be sure you're getting the best power possible without harming your engine and/or risking detonation. Finding max rpm and max EGT and then backing off from them 'a fair amount...' is one way to go to start with then keep an eye on EGT and CHT during the climb, always richen rather than reduce throttle if the temps start to get near limits, flying a bit faster in the climb can help to keep the temps down and still provide a better climb rate than flying slower and richer...

 

I've a lot more time on helis where you never lean them for take-off so others will be able to give more insights about this, cheers, Alan

 

 

[Guest Howard Hughes]

I think the moral of the story is: Never take off in a non-turbo aircraft at 8000ft with all the seats full regardless of the mixture position!

 

aka DO YOUR SUMS!!

 

 

[djpacro]

I'm imagining setting the normal run-up rpm and then adjustng the mixture to get max rpm ...... ??

Pretty much what I used to do when living at an elevation of 6500 ft with local airfields somewhat higher. Warm summers so density heights close to 9000. The airplanes generally only had basic engine instruments.

Incidentally, LSALT was 16,000.

 

 

[Sapphire]

During the "climb" he had spent a lot of time looking down fiddling with something. At that stage I already put him in the d--- brain catagory. If he actually did lean the mixture, then of course continuing on was insanity. He had one supporter who congradulated him on how well he crashed the plane, saving their lives. The earth would stop turning before I even had him for a passenger.

 

 

[facthunter]

Rough rule for leaning the mixture on a basic engine is not until the power is back to 75%. lean mixtures have a different Octane rating to rich ones.. This doesn't mean the throttle is closed from WOT but at about 4500" full throttle is about 75%. ( this is from memory check it, but I'm talking principles not numbers)

 

The basic leaning technique with no instrumentation bar a tacho is to lean it slowly till it falters and push it in till it just runs smooth and give it a bit more for good measure. You are not supposed to get detonation at the reduced power but a little bit of extra richness will run the engine cooler.. If you have a fuel flowmeter you can set the flow from MP/rpm charts. Nev

 

 

[metalman]

Good thread, I've never flown at high altitude airfields so I've only ever leaned inflight using facthunters method or MP fuel flow RPM from POH ,the high alt airfields would certainly keep you on the ball

 

met

 

 

[Sapphire]

On my Continental 0-200 I could get extra 200 fpm by just leaning a bit on a hot day. I leaned as if I was on cruise. But you want to be richer than that, so richen the mixture a bit more and listen for detonation. Somebody should come out with a recording of detonation sounds. Might even make the top 10.

 

 

[djpacro]

Good thread, I've never flown at high altitude airfields ...

I plan to visit Colorado again this year to fly in an aerobatic contest - why not join us?

[silvercity]

Regardless of the reasons why, the video clearly shows an extra long take-off run. Then when he evenually becomes airborne the aircraft follows the curvature of the earth for a couple of miles showing no sign of wanting to climb. There was a lot of clear ground the pilot could have safely landed on prior to the woods. I think the question is 'why didn't he?'

 

 

[Phil Perry]

On my Continental 0-200 I could get extra 200 fpm by just leaning a bit on a hot day. I leaned as if I was on cruise. But you want to be richer than that, so richen the mixture a bit more and listen for detonation. Somebody should come out with a recording of detonation sounds. Might even make the top 10.

" I Can't hear no, ( DA DA DAH. . ) DET - OH - NATION, ( DA DA DAH. . . ) " ? . . . [ Apologies to Mick Jagger ]