Sunday, August 15, 2010

Visual Lookout

Depending on how closely you follow NASCAR and/or the EAA Airventure (a.k.a "Oshkosh") you may know that NASCAR owner Jack Roush crashed his Hawker-Beechcraft jet during arrival at the Oshkosh event. The above link is to news coverage after the fact. The NTSB report refers to amateur video of the crash, but I haven't found it posted.

The NTSB report says:

A review of amateur video taken at KOSH showed the accident airplane in a left base turn to final for runway 18R. The airplane appeared to overshoot the runway centerline during this turn and then level its wings momentarily before entering a slight right bank simultaneously as the nose of the airplane pitched up. The airplane then turned left toward the runway centerline and began a descent. During this descent the airplane’s pitch appeared to increase until the airplane entered a right bank and struck the grass area west of the runway in a nose down, right wing low attitude.

The above, eyewitness accounts on the news, and the following description of the situation from Mark Martin (Roush's friend, former driver for Roush's team, and a pilot) suggest that he was distracted by traffic and slowed the airplane too much while manoevering for the field.

Jack got in a situation where he thought, "How am I going to get out of this without hitting somebody?" Because of all the things that were going on, which is exactly what I thought would happen, because, you know, he's in a jet and there are some very small aircraft at different speeds and those kinds of things, and he just got in a situation where he was uncertain about how he was going to make it all work, got slow and tried to get slowed down and got a little too slow and whatever.

"Stall speed," the lowest possible flying speed for an airplane, increases with bank angle, so a wing that is flying straight and level may stall as soon as the airplane banks, without a reduction in speed.

Oshkosh is an incredibly busy piece of airspace during airshow week, and they do crazy things to accommodate the rate of landing aircraft. Oshkosh arrival procedures are set up for aircraft of different speeds. Pilots choose either the 90 knot stream or the 135 knot stream, but are encouraged to fly at 90 kts if they can. The way they are handled and the spacing they are required to maintain means that Roush shouldn't have been forced to tuck in behind someone in a Cessna on final approach at 55 knots. The NTSB video analysis and eyewitnesses don't mention conflicting traffic. The standard VFR arrival is a right base for a combined final to 18L/18R, with the air traffic controllers directing aircraft left and right. On the left base arrival he was supposed to turn left base directly towards the blue dot, partway down the runway. If he was late on that turn he could have put himself into conflict with arriving slower traffic. We do know his final turn was late so he was slightly past the final approach course where he was supposed to be, right of the centreline on runway 18R, further from traffic on 18L, and towards a shaded "do not fly" zone over airshow guests. I wonder if another aircraft was arriving on a right base for a different touchdown spot for 18R and that was an issue. My internet connection here isn't good enough to download the full NOTAM pdf, or to find some stall speed numbers on the airplane he was flying. The runway "18R" on which he was cleared to land is normally just 18, and runway "18L" is a taxiway the rest of the year. Amusingly the media are calling it "runway 1836" perhaps after NOTAMs or airport signs that would call the piece of pavement "runway 18-36" after its two ends.

Another source, which I don't recommend you click because it is making my computer screen flash--I think it's trying to load pop-ups--states that Mr. Roush was initiating a go around right before the crash. I think that may be just because he went to full power in an attempt to recover from the stall. Mr. Roush doesn't mention that in his description, "Basically a landing accident, based on a conflict in airspace with another airplane, after I'd been given clearance to land."

I assume he was flying with the 135 knot contingent, and not the 90 knot aircraft. I wouldn't try to do an arrival at 90 kts in my bird. It's theoretically possible, but not safe.

The article that caught my attention was this one, with a pull quote from Roush claiming that there is no FAA restriction on private pilots with monocular vision, "except maybe airline pilots." I believe one-eyed US pilots do have to demonstrate ability to compensate, but after that, they can become airline pilots.

ICAO medical standards require binocular vision, but "flexibility based on national experience may be applied," so Canada makes an exception for the licensing of monocular vision private pilots, and on a case-by-case basis, sometimes with restrictions for commercial pilots who lose vision in one eye.

This is Roush's second airplane crash. His first was a crash of an experimental homebuilt into a lake, an accident which the NTSB attributed to "the pilot's decision to fly at low altitude and his improper visual lookout resulting in an in-flight collision static with wires."

He had two car crashes as a racing driver, too. I could say he just lives fast and takes risks, but overshooting the runway centreline when he was already slowed to below his normal approach speed suggests that he didn't have exceptional control of the airplane. Considering the quantity of recording equipment and witnesses involved, there's lots to work with to determine what happened. I'll be interested to see the full report when the NTSB completes their investigation.


Sarah said...

It's an interesting one, from the standpoint of ATC/pilot interaction, esp, at Oshkosh.

Here are stills of the moment of impact which don't really shed any light on why this happened. They're spectacular, though.

Sounds to me like he got cramped, rushed, and pushed into an unstable approach that went bad.

There is ATC audio on the website, which I can't link to. You have to register. But here is my very unofficial transcript. Times are relative to the clip.

00:06 ATC 6Jr left base 1 8 right clear to land, wind 200 niner gusts 18
..... 6JR left 1 right .. 1 8 right uh clear to land 1 8 right 6 JR
00:16 ATC and premier, uh make your best turn abeam the tower
.... 6JR base turn abeam the tower 6 JR
00:25 ATC premier you can turn northbound on the downwind
00:37 ATC lake on the ... uh disgregard
00:44 ATC Lake south of uh oshkosh ah. are you inbound for 1 8 right rock your wings
00:51 ATC Lake, make a right hand turn maintain 1800 crossing the departure end of 1 8 right enter left downwind 1 8 right
01:01 LAKE left downwind 1 8 right
01:20 6JR is 6 jr going to be ok with this
..... ATC affirmative
01:24 6JR I don't think so
01:30 ATC lake start your descent enter the downwind uh turn your base abeam the tower clear to land on \
the uh pink dot
01:41 6JR goinem (unintelligible: going around? )
01:47 ATC alright premier jet use caution for the uh traffic ahead on the upwind and uh..
02:03 ATC alright Lake, go around
.... LAKE Lake going around
02:13 ATC and aircraft entering the downwind rock your wings expect to go around

lahso said...

I thought that binocular vision applied only within a couple of arms' lengths — after that, we use other cues (size, shadow, fading of colours) to determine distance.

If I'm remembering correctly, monocular vision might affect the ability to grab a lever or knob on the panel, but not to estimate the height for flaring a jet.

Sarah said...

D'oh. I see the ATC audio is on the avweb page I linked above, the one with the photos. Disregard the useless transcript.

GPS_Direct said...

Those photos on AvWeb are quite the sight!

I was up there two days later and talked with some P-51 guys and the consensus was that he got cramped for spacing following the Cessna.

It wasn't -too- busy (for OSH anyway) at the time and the weren't using 18L, just 18R. But, normal procedure at OSH is to vacate the runway onto the grass to clear the way for following traffic. With the heavy rains the weekend before the show, much of the grass was swamp, and they were sticking to hard surfaces only.

So, it's possible the spacing would have worked if the Cessna could have vacated as usual (and maybe the controller was expecting that). But JR didn't like the looks of things (as evidenced in the recording), and tried for a go around but the engines weren't spooled up.

Why he was flying the standard arrival pattern is also in question, as I would have expected him to fly the "turbine/wardbird arrival" which is used by the faster planes needing more room, straight in approaches, and full-length runways.

Of course, it wouldn't be OSH without somebody dinging a plane. Fortunately, no fatal accidents this year at the show.

Ron said...

I'm sure you just simplified it for the non-aviators in the audience, but it might be worth pointing out in this instance that "stall speed" is not the slowest speed at which an aircraft can fly.

It's the speed at which, under a 1G load, the wing will reach the critical angle of attack.

If you lower the loading to less than 1 G, the aircraft will reach critical angle of attack at less than the traditional "stall speed". Lower it to zero G and the aircraft will have no stall speed at all, as it will not be able to reach the requisite AOA.

Likewise, ramp up the Gs and the critical AOA will be reached at a higher airspeed.

I bring this up because it's a common (and dangerous) misconception among pilots. Any aircraft can be stalled at any airspeed and/or attitude.

As for Rouch, I find it interesting that he asked a controller "will 6JR be ok with this?". There's only one person that determines such a thing: the pilot. I don't understand why he was asking such a question. If he had concerns he should have aborted the approach.

Aviatrix said...

Ron: I was referring to the stall speed corrected for attitude and you to the published wings level zero G stall speed, which is why I said it increased with bank angle.