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Cessnaflyer

The dangers of density altitude

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Warning this is a graphic video at the end but it shows the dangers of density altitude very well. I used to fly in this area quite a bit when I was teaching and want to show the dangers of density altitude.

 

This occurred at U63 in Stanley, Idaho which has a 5,000 foot runway that you can see him using all of and more.

 

http://www.liveleak....=835_1344412426

 

There are many links in the chain of events that broke here:

 

High density altitude:

The first clue not to fly this day is a hot and high airport. The U63 airport is at 6,370 feet which on a normal day is a fairly high airport add on to it the temperature of 27 C and you have problems. I always like to have my students do little density altitude problems even in the winter and it was always a big shock to them. The airport that I usually taught at had an elevation of 2,400 feet. The average winter temperature is -5 C. This would still give a density altitude of 529 feet MSL, not high but everyone was amazed air density was still higher than at sea level. In the summer time the airport was averaging at 35 C. This would give a density altitude of 5187 feet. For this accident at U63 the density altitude was 9139 feet! Normally aspirated powered aircraft have a hard time operating at this altitude.

 

Loaded over gross:

The aircraft was a Stinson 108 which has all of around 200 horsepower depending on what engine is installed. In the backcountry this is a very underpowered aircraft. When you add 3 more people, gear and fuel to get yourself out, you are well over gross weight.

 

Engine mismanagement:

In the video it can be seen that he is flying with a full fuel mixture. This kills performance because you are flooding the engine with too much fuel to get a proper fuel/air ratio and the correct burn. This can reduce power by 50% or more. Because there is less air to burn you need to put less fuel to keep the proper stiochiometric mixture and maximize power output. Not only were they trying to fly in a high density altitude, overweight he was trying to do it with only 50% power.

 

Here is the preliminary report on the accident. More will be revealed most likely next year when the full report is published.

http://www.ntsb.gov/...701X65804&key=1


Chris Miller

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That brings up a question. Why do aircraft rely on carburetors with manual mixture controls in this day and age? Sure certification is more severe than auto, but is it really so hard to fit electronic managed fuel injection? Or is it just that there are a lot of old aircraft out there?

 

scott s.

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That brings up a question. Why do aircraft rely on carburetors with manual mixture controls in this day and age? Sure certification is more severe than auto, but is it really so hard to fit electronic managed fuel injection? Or is it just that there are a lot of old aircraft out there?

 

scott s.

.

 

Even fuel injected aircraft you still have to manage mixture.

 

The reason that you don't see many airplanes with electronic fuel management is that it is very expensive to certify. There are only a few aircraft like the Liberty XL2 with a FADEC and aircraft that are being fitted with the Rotax engines and their altitude adapting carburetors


Chris Miller

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3 Blokes in a little airplane at that altitude on a hot summer day???

 

Nice catch with the mixture as that would have made a difference.

 

I have been flying around ORBX new KJAC scenery with the Carenado Cessna's and that has been a fun challenge. But at least my sim resets itself if I can't get off the ground or climb. Fun to play around with.

 

The other high altitude airport to play around with in the flight sim is Big Bear in California.


Matthew Kane

 

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My other thought is the Pilot is injured but his passengers walked away. Not a bad outcome and he learned a hard lesson from that one.


Matthew Kane

 

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My other thought is the Pilot is injured but his passengers walked away. Not a bad outcome and he learned a hard lesson from that one.

 

The scary thing is that he had a commercial license. You can tell they hand out certificates like candy at a parade here.


Chris Miller

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The scary thing is that he had a commercial license. You can tell they hand out certificates like candy at a parade here.

 

Surely you wouldn't be surprised by how many "Santa Clause" DPEs there actually are.


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Zachary Waddell -- Caravan Driver --

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Surely you wouldn't be surprised by how many "Santa Clause" DPEs there actually are.

 

There are a few!

 

A lot of pilots out here on the islands would go to Las Vegas to do their ATP checkrides. The DPE these pilots went to was one of them that would hand out licenses! The DPE got busted and anyone that took a test under him got a letter telling them to stop flying and that their license was invalid. Really sucks for the ones that were good pilots but just happened to have been dealt this particular DPE.


Chris Miller

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There are a few!

 

A lot of pilots out here on the islands would go to Las Vegas to do their ATP checkrides. The DPE these pilots went to was one of them that would hand out licenses! The DPE got busted and anyone that took a test under him got a letter telling them to stop flying and that their license was invalid. Really sucks for the ones that were good pilots but just happened to have been dealt this particular DPE.

 

Similar story around here, but it's an ongoing issue... :mellow:


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Zachary Waddell -- Caravan Driver --

Facebook: http://www.facebook.com/zwaddell

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After running out of "runway" it should have been crystal clear that an abort was mandated...

 

I simply cannot fathom why the pilot continued trying to takeoff.


Fr. Bill    

AOPA Member: 07141481 AARP Member: 3209010556

Interests: Gauge Programming - 3d Modeling for Milviz

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After running out of "runway" it should have been crystal clear that an abort was mandated...

 

I simply cannot fathom why the pilot continued trying to takeoff.

If he had the presence of mind to abort the takeoff, he would have also conducted proper pre-flight planning and not tried to takeoff to begin with!

 

It is clear as day during the takeoff roll that it doesn't want to fly.

 

Best regards,

Robin.

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I simply cannot fathom why the pilot continued trying to takeoff.

 

Yeah that was bizarre... I could not believe it either Fr. Bill.

 

A number of links mentioned (mixture, over gross, DA) in this accident chain that, if any broken, might have prevented the accident from happening.

 

Note that (from what I could tell) the pilot did not continue increasing pitch to the point he stalled in... "better to crash under control, than out of control".

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Also, he had several minutes after "takeoff" where there was plenty of open ground on which to attempt a landing...

 

...long before he reached the treeline! It was quite obvious by then that the a/c was barely out of ground effect, so again... it's truly some bizzare thinking going on. :blush:


Fr. Bill    

AOPA Member: 07141481 AARP Member: 3209010556

Interests: Gauge Programming - 3d Modeling for Milviz

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It is clear as day during the takeoff roll that it doesn't want to fly.

Reminds me of that 'uncool pilot' saying, even with just being a sim pilot myself. The 'uncool' guy may have missed all the preflight stuff on the impact of altitude plus high temps, but he would have aborted the takeoff as long as he could. At 1:01 she even bumps back to the ground, rolling/trying for over a minute.

 

I've read a bit into the comments on that video and while there is a lot of typical comment stuff, one points out that the pilot was doing something on his iPad just before hitting the trees. I first thought the comment was a joke, but the slow motion shows it. Can't believe it. Not saying he was playing angry birds, but I guess the eyes and mind should have been on the plane and the fact that trees are flying pretty high these days. Yikes!

 

With all the points from Chris' post and that attitude, I guess he had it coming. But why? That's the part I don't understand. The only purpose this flying attempt ever had was to end up as a training video on how to not do it.

 

Glad they made it but they should ask the pilot some serious questions, just because he was lucky.

I wonder what the passengers thought, means where that mental tipping point took place from 'we are (just) flying to another field' to 'something is very wrong here'. Uncomfortable mood, even thinking about it.

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