NASA Study: Wing Stall Theory May Be Wrong

A NASA video circulating on the Internet suggests conventional wisdom is wrong: that an ice-induced wing stall brought down the Continental commuter near Buffalo.

Instead, the video suggests not a wing stall but a tail stall may have caused the crash.  And if tail icing is really the root cause, it means both the automatic system AND the pilot applied exactly the wrong recovery technique; thereby dooming the flight!

As a 31-year veteran pilot, I can tell you pilots are generally trained to deal with problems associated with engine and wing icing.  Rarely is tail icing ever mentioned as a significant problem.  This study suggests it should be.

The twenty-three minute video shows both wind tunnel and in- flight icing tests that suggest turbocraft aircraft similar to the Q-400 commuter that crashed in Buffalo, are particularly vulnerable to tail icing.  Worse, it urges recovery techniques for a ice-induced stalled tail should be exactly opposite to recovery techniques for a wing stall!

Recent reports from the crash investigation say when the problem was encountered the automatic system pushed the controls forward and the pilot added power, but if the conclusions of the NASA video are correct, the pilot should have aggressively pulled aft and use little if any power.  The test pilot in the video lost only 300 feet of altitude recovering from the problem.

You can find the video at:

http://video.google.com/videoplay?docid=2238323060735779946

Pilot May Have Over-reacted

Pilot error may be the root cause in the crash of the Continental commuter outside Buffalo, NY.

Late reports say NTSB investigators are apparently interested in precisely how the pilot reacted to aircraft warnings that a wing stall was imminent.  Reports say the aircraft “stick-nudger” attempted to push the nose downward in a proper attempt to restore sufficient airflow over the wings, but the pilot may have wrongly overrode the safety system; all but guaranteeing a crash.

Bird Strikes Pilot in the Face

Another birdstrike!

Scarcely a month after US Airways was forced to ditch an airliner in the Hudson River following an encounter with Canadian Geese, the pilot of a twin-engine charter plane got smacked in the face when a turkey vulture crashed through the aircraft windshield in flight!

In fact, the impact was so hard that the carcass of the bird was still impaled on the windshield after the craft was safely on the ground at Ft. Lauderdale International in Florida.

Captain Jay observes that seasoned pilots know birdstrikes are fairly common.  What is unusual in these incidents is that they both involve very large birds causing spectacular damage.

No passengers were reported aboard, and the lone pilot was not injured.

White House Halts FAA Safety Directives

A Wall Street Journal report suggests the Obama administration may have interfered with the normal flow of FAA Air Safety Directives  (known in the industry as “ADs”).  An Air Transport Association industry publication summary of the story follows:

White House transition halts routine FAA directives
A White House memo ordering federal agencies to stop implementing leftover regulations from the Bush administration appears to have blocked the FAA from issuing airworthiness directives for about two weeks. The agency normally generates 30 or more safety orders every month, but only four such orders have been issued since Jan. 23. Following clarification by Transportation Secretary Ray LaHood, the directives have started flowing again, and a spokesman for the Air Transport Association says “maintenance programs have not been interrupted” by the glitch.

Canadian Geese Caused Crash

The New York Times is reporting investigators have determined Canadian Geese were ingested in both engines of the US Airways A-320 which ditched in the Hudson River a month ago.

The New York Times ran an interesting piece telling how investigators are working to pinpoint the exact species of bird.

FoxNews Anchors Bill O’Reilly and Geraldo Rivera conceded their theory that the plane was downed by compressor stalls was wrong  (see “Engine Stalls Down US Airways Jet” blog post below).

Commuter Crash Update

Evidence is mounting that icing had everything to do with the crash of  Continental commuter flight 3407 outside Buffalo, New York.

The NTSB says the crew properly employed anti-icing during the approach, but they failed to disconnect the autopilot upon doing so; a practice discouraged by most operators.  At some point the pilots received warning that a wing stall (loss of lift) was imminent.  This caused the auto-pilot to disengage at a critical moment.  The aircraft suddenly began pitching and rolling violently and dropped 800 feet in 5 seconds, finally crashing belly-first atop a house, facing the opposite direction of flight.

Aviation experts are also questioning the effectiveness of the rubber “boots” commonly used  to break away ice away from wings of turboprop aircraft, versus turbojet anti-ice systems which typically use hot air to heat wing surfaces.  One can quibble whether one system is superior to the other, but bottom line is we don’t see as many crashes like this one involving jets.

Passengers prefer jets, but airlines often use turboprops for commuter service because the latter get 30% better fuel efficiency over turbojets.  But if balanced solely against high fuel costs, a jet’s speed and comfort advantages seem less important to operators on short flights.