Airliner may have risked fatal stall

MD-80s disbelieving passengers told everything was all right By Don Phillips WASHINGTON POST

Feb. 19  Richard Aussicker was relaxing in his aisle seat as Spirit Airlines Flight 685 cruised toward Detroit on Jan. 30 when he sensed a growing vibration throughout the cabin. Louder and louder, he remembered, almost like driving down one of those washboard roads. The plane dived precipitously, but leveled off. Then came more vibration and another dive.

WE THOUGHT we were all going to die, said the Wyandotte, Mich., mechanic. I never saw so many people get so close so quickly. Passengers screamed and prayed. One woman began praying loudly for the souls of everyone on board. A man shouted at her to shut up. A flight attendant ran down the aisle saying, Oh, my God. What Aussicker and the other passengers of the Fort Myers-to-Detroit flight did not know was that they probably came as close to falling from the sky in an aerodynamic stall as any airline passengers have ever come without dying. In a stall, airflow over the wings is disrupted, destroying lift and causing the plane to fall. But stalls at normal cruising speed are almost unheard of. On Flight 685, the pilot inexplicably flew the plane too high for its weight, sources close to the investigation said. Passengers said the captain then blamed the harrowing dive on turbulence. When the plane landed, the crew then failed to notify airline mechanics that they might have overstressed the engines in recovering, according to the airline and federal investigators.

COMPLAINTS GROUNDED PLANE

The plane, a McDonnell-Douglas MD-80, flew two more passenger-carrying flights with the possibly damaged engines before a flood of passenger complaints prompted the airlines chief pilot to do some sleuthing to get to the real story. The airline then grounded the airplane for a thorough engine inspection. Greg Van Brunt, Spirits vice president for maintenance control, said the pilot has been suspended with pay, as required by the airlines contract with the Air Line Pilots Association, pending a hearing between the company and the union. Sources close to a federal investigation of the incident said it is possible that the Federal Aviation Administration will suspend or revoke the captains license. Spirit, a low-cost airline based in Fort Lauderdale, Fla., that flies to 14 cities, would not identify the captain or the co-pilot.

Many questions are left unanswered, including why an experienced captain would make such a basic mistake and then compound it by failing to report what happened. The story, pieced together from passengers, airline officials and sources close to the investigation, began when the plane was about an hour and a half from its destination. Cruising at 31,000 feet, the plane was cleared to 35,000 feet, although airline officials said they are still unsure whether air traffic controllers offered the higher altitude or the captain asked for it.

SEARCHING FOR ANSWERS

The plane, however, was too heavy for any altitude over 31,000 feet. Pilots have performance charts that allow them to calculate their maximum altitude at any point during their trip. The maximum altitude is dependent on weight, which decreases as the aircraft burns fuel. Exactly what happened is still subject to investigation. But the vibration felt by Aussicker and other passengers was probably a stall buffet  the airflow over the plane beginning to break down before a deep stall, in which the airflow breaks down completely and the wings have no lift. As an aircraft flies higher, an odd aerodynamic phenomenon occurs that old-time pilots used to call the coffin corner. As the air becomes thinner, it is possible for the aircraft to stall if the pilot tries to go just a little faster or just a little slower. By going just a little faster, the aircraft may surpass the speed of sound at that altitude, causing it to stall because at that speed commercial airline wings are not designed handle the turbulence created. By going a little slower, the aircraft can enter a low-speed stall for lack of sufficient airflow. Even a bump of turbulence or a turn can bring on a stall buffet.

This is where the weight of the aircraft comes into play. The heavier the plane, the narrower the range of acceptable speeds at any given altitude, which is why aircraft are subject to strict weight and altitude limits. Stalls almost never occur on commercial aircraft because of early-warning systems and because pilots can usually feel the stall buffet coming on.

THOUGHT WE WERE GOING TO DIE

After the event, the Detroit Free Press interviewed numerous passengers, who were mystified by what had happened. They all told basically the same story. Flight attendants yelled they have to sit down, Ann Jara of Westland, Mich., told the Free Press. One went down the aisle saying, Oh, my God. The shaking and noise went on a couple of minutes, then dead silence. We really thought we were going to die. Several passengers mentioned a loud engine noise. The airline said the crew had pushed the engine throttles to overthrust  stressing them beyond normal limits, a move pilots call going to the firewall. The plane descended rapidly and leveled off, apparently still too high for its weight, necessitating another rapid descent. Under FAA rules, a pilot must report firewall incidents so mechanics can check for engine damage. The crew of Flight 685 did not do so, according to investigators. There was no notation in the aircrafts maintenance log, as required. After the second dive, Aussicker told The Washington Post, a flight attendant announced over the public address system, Sorry, I cant answer any questions, but the captain says everything is all right. A little later the captain announced that the incident was due to some clear air turbulence that set off an improper stall alarm, Aussicker said. Flight attendants then did everything they could to pretend nothing happened.

EXPLANATION DIDNT FLY

Almost no one on board believed the explanation. Aussicker e-mailed a letter to the airline and many other passengers called Spirit to complain. After so many passenger complaints, Van Brunt said, the airline began interviewing other employees. The chief pilot began quizzing the captain, and the story came out, Van Brunt said. Advertisement

We immediately grounded the airplane, he said. After a preliminary check of the engines, a crew flew the MD-80 without passengers to a maintenance base in Miami for a more thorough check. No damage was found and the plane is back in service, he said. Van Brunt said the airline then called in the FAA for an investigation that is continuing. Spirit Airlines is one of the handful of no-frills airlines that survived in the years after the May 11, 1996, ValuJet crash in the Everglades. Spirit has turned a profit every year but one since its founding in 1992. The airline was founded in Eastpointe, Mich., near Detroit, as an outgrowth of Charter One, a charter carrier founded in 1980 that mainly flew gamblers and tourists to Atlantic City. Today, it has evolved into a low-fare scheduled airline that flies to 14 cities with 16 twin-jet MD-80 aircraft and nine DC-9s, with plans to expand to the West Coast. Spirit moved its headquarters to Fort Lauderdale last year. Van Brunt said the airline has sent bulletins to all Spirit pilots warning of the dangers of high-altitude pitch-up, and may consider other actions. This is outside the scope of normal operations, he said. This is something we never had happen before. Aussicker is also rethinking his initial opinion of the flight crew. I thought they saved our lives, he said. I wanted to thank them. But the crew was nowhere to be seen as he left the aircraft.

-- Hawk (flyin@high.again), February 20, 2000

Answers

YIKES!!!

Having done a bit of piloting myself I've always been a little touchy when freaky little things happen while on commercial flights but not enough to stop taking them. Think I'm going to do a John Madden and stay on the ground. This is getting really freaky!

-- granny-TX (westamyx@bigfoot.com), February 20, 2000.

Wow! What do you make of this one?

-- Carl Jenkins (Somewherepress@aol.com), February 20, 2000.

The way the passengers describe the plane porpoising sounds to me a lot like the stabilizer problem again. I wonder if they were on autopilot when it happened. The pilot was obviously trying to downplay the danger to protect the reputation of the airline, and keep his job.

-- Hawk (flyin@high.again), February 20, 2000.

Just don't know what to make of this. It seems that we have incompetence and/or irresponsibility or the "who cares???", etc., etc., permeating just about every area of life these days. Running into someone who is truly competent or genuinely caring and sincere about their task/job/duties/etc., is getting to be a rare experience. When it does occur it's really hard to trust. My Veterinarian's husband used to go by the Nissan place after we had service to make sure they "did us right". He started doing that years ago (he worked there for years). Makes me a little nervous every time I have something important done on one of the vehicles. Could go on and on. After so many years experiencing the "don't give a sh*ts" from various auto shops, makers, corporations, etc., I don't see any reason we should expect more from airline employees. Pretty sad and scary. It's everywhere.

Although I am a "doomer" it's getting harder and harder to be an "eternal optimist"="something worthwhile can come of this or a valuable life lesson can be learned" (that is NOT the same as Pollyanna) Peace

-- granny-TX (westamyx@bigfoot.com), February 20, 2000.

The explanation of a stall due to overweight at a high altitude makes sense. The passengers description matches that of a stall at lower altitude. Th fact that it was repeated illustrates the very small envelope that the aircraft had available to manouver in under the flight conditions. Under such conditions even moderate turbulence could have initiated a stall. Stalls and recoveries are practiced at lower altitudes during training where the aircraft has a much larger envelope in which to operate. My old Globe Swift used to shake like a wet dog when it got close to

-- Roy (bushwhacker @ north woods.com), February 20, 2000.

The word stalling got cut off my preceding post.

-- Roy (bushwhacker@north woods.com), February 20, 2000.

All that extra non-compliant date data in the buffers of the non- compliant chips weighs a lot. In this case, the buffers didn't explode but the data was vibrating causing the aircraft to seem like it was in a stall buffet.

Tongue-in-cheek mode off.

-- Mikey2k (mikey2k@he.wont.eat.it), February 20, 2000.

Incidents like these used to happen every now and then with DC-4,DC-6 recips and into the jet age with B-707 and DC-8 years before computers or imbedded chips were even put on board. High and low speed and altitude stalls have been happening ever since Orville and Wilbur decided to go for a spin.

-- John Thomas (cjseed@webtv.net), February 20, 2000.

Stall buffet will rattle the fillings out of your teeth. In the cockpit it'll render the instrument panel a blur. You have to fly out of it by instinct: push the throttles full forward and nose over. You worry about overspeeding the engines once you're back under control or on the ground.

Why would the pilots be trying to climb higher, though? Strange thing about jet aircraft operations, the higher you can fly the better your fuel economy and your ground speed increases while you fly the same airspeed. Airlines put great emphasis on trying to maximize the fuel burn of their flights and this crew was probably trying to follow their company's policy.

This one is a case where the crew's efforts didn't pay off and now they're goats. If they had managed to do it, they would have arrived on-time with a one or two percent fuel savings and been praised by their supervisors.

WW

-- Wildweasel (vtmldm@epix.net), February 20, 2000.