Words of Advice:

"If Something Seems To Be Too Good To Be True, It's Best To Shoot It, Just In Case." -- Fiona Glenanne

"Flying the Airplane is More Important than Radioing Your Plight to a Person on the Ground
Who is Incapable of Understanding or Doing Anything About It." -- Unknown

“Never argue with stupid people, they will drag you down to their level
and then beat you with experience.” -- Mark Twain

"Stay Strapped or Get Clapped." -- probably not Mr. Rogers

"Eck!" -- George the Cat

Sunday, August 12, 2012

An Aircraft Loaded With Fail

By now, you may have seen news coverage of the Stinson that was crashed into trees after takeoff from the Bruce Meadows Airport in Stanley, Idaho.

If there was ever a crash that didn't need to happen, this one was it.

Bruce Meadows Airport (U63) has an elevation of 6,370' MSL. According to AccuWeather, the temps that day were in the low 80s.

That puts the density altitude somewhere between 9,000' and 11,000'. To put it succinctly, density altitude is the altitude that, aerodynamically, the airplane sees.

The pilot had the mixture control knob at the "full rich" position. This can be seen both as they taxi out and, in the slow-motion video, as the plane tumbles through the trees.
That is the appropriate setting for sea level to maybe 3,000'-5,000'. Above that, the technique for taking off is to set the brakes, run the engine up to full RPM, and then lean out the mixture until best power is achieved. That way, you'd get about 75% of the maximum rated horsepower, assuming that the engine was in tip-top working order.

A 108-3 Stinson (which is what that was) came from the factory with a 165hp engine. At that density altitude, it could be expected to put out 123hp. With a full-rich mixture setting, the engine was running over-rich and was probably not even close to making full power.

The takeoff roll went on damn near forever. It was pretty clear from the video that the wisest course of action would have been to pull back the throttle and abort the takeoff or, after staggering into the air, land. There was plenty of room to do so, it was obvious that the airplane wasn't climbing worth a fart. But the pilot pushed on. And the airplane did all that it could be expected to do under the circumstances: It flew all the way to the scene of the crash.

I'm not even going to get into the point that on launching from a high-altitude airstrip on a hot day, all of the seats in the airplane were full with adult males. But I will note that if that airplane had been equipped with shoulder harnesses, the pilot's injuries would have likely been a lot less severe. The FAA makes it easy to install newer seatbelts and shoulder harnesses into older airplanes. You don't even need a STC or a Form 337 to do it, it's just a logbook entry by a mechanic. A shoulder harness may not fit the look for some classics, but better that there be a little bit of farb in the airplane and you don't eat the instrument panel in a crash.

4 comments:

Eck! said...

High, Hot, and Heavy, that is a bad thing if your not awake enough to realize the aircraft WILL NOT perform well.

I've done that but with the caveat of knowing it was going to be sluggish and leaned the crap out of it. Things went fine but, I was prepared to abort in any hiccup however trivial. I was not more than 1000ft MSL and it made a big difference.

How is it that nearly 32 years after the mandate for shoulder harnesses this plane didn't have them? That is 32 annual inspections that were incomplete!

Std male adult is 170 pounds times 4 is 680
pounds plus fuel, baggage, that plane was likely
overweight as well.


Eck!

Comrade Misfit said...

Front seat shoulder harnesses are not mandatory for any airplane manufactured before 7/19/1978 (12/13/1986 for rear seats). The previous owner of my airplane didn't have them in. The first thing I did when I bought it was to have them installed for the front seats.

Phil said...

People that operate machinery--particularly machinery that moves at high speed--ignore physics at their own peril.

Sarah said...

Good call on the shoulder harness. All our club planes are refitted.

This video has really taken off... it made newspapers and TV I hear. Wonder how the pilot feels about his 15 minutes of fame?

No doubt pretty embarrassed. He must have gotten away with some marginal takeoffs in the past and pushed this one just a little too far.

I am impressed with how well the 108 did with 165 HP. Our old 160hp c172 struggles a little at max gross with 2000' DA.