NTSB Says a Downdraft Killed Steve Fossett

jd writes "The National Transportation Safety Board has now released the text of its examination (full narrative available) into the crash of Steve Fossett's aircraft on Sept 3rd, 2007. It concludes that downdrafts were the likely cause of the crash, dragging the plane into the mountain with such force that, even at full power, it would have been impossible to escape the collision. Pilots experienced in the area report that those winds can rip the wings off aircraft; and Mark Twain remarked that they could roll up a tin house 'like sheet music.' One must wonder why such a skilled aviator was taking a gamble with such hostile conditions, given that he was looking for a flat stretch of land to race cars on, but that is one mystery we shall probably never know the answer to."

Comments

NTSB is wrong

[Em Emalb]

Sudden deceleration is what killed him.

Re:One must wonder ...

[DoofusOfDeath]

One must wonder ...

...how pilots experienced in the area and are still alive know that these downdrafts can rip the wings off an airplane?

Yes, it's odd. Almost as though they can somehow communicate amongst themselves or even read NTSB reports.

Yes... this definitely is something we need to understand better.

Mountain Wave Action

[Nobo]

The proper term for what they're describing is a mountain wave or wave action. http://en.wikipedia.org/wiki/Lee_wave contains a good description of the effect.

Mountain waves can be felt in small piston powered aircraft even flying significantly above the tops of the mountains, even several thousand feet above the peaks on either side of the valley you're crossing.

If you're holding altitude, you see that you speed up when you're crossing falling terrain and slow down when you're crossing rising terrain -- because as you cross the rising terrain, you're in the downdraft and so to maintain altitude, your airplane "feels" like it has to climb to stay at the same altitude in the falling air. Climbing requires additional power over simple cruise flight, or you slow down.

I've seen airspeed of an aircraft that should cruise at 150 knots, range from 90-180 knots, depending on whether you're on the uphill or downhill side of the wave. In severe conditions, you just cant' maintain altitude without slowing down too much, and you have to vary altitude to ride the waves.

It can be a scary experience knowing you don't have enough power to out-climb the wave -- That's the reason that you typically fly significantly higher in the mountains, even with good visibility -- You're not worried about hitting the mountains because you can't see them, you're worried about getting sucked by these waves and not having enough altitude to ride them out.

Re:Mountain Wave Action

[smellsofbikes]

Mountain flying is technically challenging -- as challenging for an experienced pilot, as just flying is for a person who doesn't know how to fly. There are a lot of things you do when you train in mountain flying to minimize your risk, but if you're in a small piston-engined plane, there are a lot of places where you just don' t know what the best plan is, so you have to make a quick decision and hope you were right.
First off: fly down valleys, not up them. That's not always possible, though: you sort of have to fly up one valley to go over the pass and fly down the next. Another is you don't fly up the middle of a valley. You fly up one side, so that you have room to make a quick turn if you find that you're in a narrow bit of the valley and you need to get out. But here's the tradeoff: there are sometimes strong upslope/downslope winds along the valley sides, so by preserving your ability to turn, you might run into an intense downdraft. (Generally, winds are faster, the higher you go, but in valley conditions, downslope winds known as foehn or scirroco winds tend to be intense right around the valley itself, particularly if you're flying up an old glacial valley with hanging valleys intersecting it: there are these big cold air currents flowing down them just like water would and pouring down into the main valley.)
Likewise, once you're in a downdraft you have to make some hard decisions. You pull the nose up to best angle of climb, full power, and you hold it. What if you're aiming right towards a big rock? If you turn, your stall speed increases, and you're already fairly close to stall speed, so you have to weigh reducing your angle of climb (which in a microburst or downdraft means increasing your speed towards the ground) to make the turn, vs. trying to ride out your current heading and hoping you'll miss that big object. You don't know, a priori, which one is going to work. Maybe you'll break out of the downdraft. Maybe it's worse over there where you're about to turn. That's where skill, experience, and lots and lots of luck come into play.
Where I live, sometimes the clouds from the mountain waves are visible in long rows at over 25,000 feet elevation, in lines for a hundred miles downwind of the mountains themselves, and every one of those is strong enough to shake a plane like a ragdoll. A B-52 bomber had its vertical tail ripped off and lost part of a wing in clear air turbulence 5000 feet above the nearest mountain.

Re:SO uh, when did Mark Twain have a plane?

[JaneTheIgnorantSlut]

Just thought I'd ask.. me thinks Mark Twain died before the aircraft age.

Reports of his death were greatly exaggerated.