Those who have been following this aviation blog will recall the chilling video that formed the nucleus of the post, 'The Fatal Stall'. In this instance, the aircraft involved was a light aircraft, but in recent times the tragic demise of Air France 447 has reinforced that size is not a barrier to the lethal nature of the stall. And yet, despite the publicity, Air France 447 was not the only airliner to fall victim to the edge of the aerodynamic envelope. Below is the story of another airliner that was lost.
Air France 447 was not the first.
The Boeing 727 is one of the all-time classic airliners. Built for speed, it is a pilot’s
Prelude to Disaster.
The sector should have been little more than a milk run. The flight was a short positioning sector from New York’s JFK Airport to the upstate town of Buffalo where an American football team and its staff were awaiting a ride back home. The crew of three were the only
As the crew readied the Boeing, the forecast for the night ahead was typical of a cold winter’s eve on the east coast. The cloud base sitting at around 5,000 feet with occasional thunderstorms extending towards 30,000 feet and icing virtually assured for all levels in between. The crew had planned to cruise above the weather at 31,000 feet and had very little reason to believe that the flight would be anything other than routine. And yet in less than 15 minutes after departing JFK they would crash to earth in a forest a mere twenty miles to the north. But how?
Air Traffic Control’s first indication that a problem existed for Flight NW6231 came in the form of a Mayday call stating that they were, “...out of control and descending through 20,000 feet”. In response to ATC’s transmission, the crew’s final message was that they were, “...descending through 12....we’re in a stall.” In less than a minute they were dead.
The Boeing had hit the earth at high speed and its wreckage was confined to an area less than 50
Much more would be revealed when the aircraft’s Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) were
Incredibly, as they climbed the indicated performance was astronomical with a speed of more than 400 knots and 6,000 fpm rate of climb as the aircraft punched through 20,000 feet.
On the verge of 25,000 feet, the crew
The aircraft continued its downward plunge and at around 12,000 feet the Captain
IMAGE: The Ed Coates Collection
The attitude indicators were frozen at 20 degrees nose down at the point of impact, but it was what they were indicating a few minutes earlier that was crucially overlooked. Climbing through 16,000 feet when the incredible climb performance first began to accelerate, the pilot’s action was to increase the back pressure in an attempt to arrest the blistering speed. If due attention had been paid to the aircraft’s attitude, the nose was actually more than 30 degrees up, when a more likely attitude was in the realm of five degrees. Continuing to pull back only exacerbated the issue until the critical angle was exceeded and the aircraft stalled. So began the aircraft’s rapid fall to earth, but even so, there was no attempt to roll off the high bank angle as the aircraft descended so that any back pressure on the control column merely served to increase the G-loading. Everything was working against the crew possibly recovering the
But why would the crew receive such phenomenally high airspeed indications when in fact the aircraft was stalling with a high nose attitude and the thrust levers were closed? The simple answer is that the pitot heat had not been selected prior to take-off and the multiple probes had iced up until they were blocked passing 16,000 feet. The Cockpit Voice Recorder (CVR) revealed that there had been some hesitation,
The Lessons Learned.
For such a tragic outcome, the findings revealed that it was the failure to successfully complete a checklist that created the problem and an undue focus on airspeed rather than aircraft attitude that led to disaster.
The need for checklist discipline, whether for the lone pilot or the airline crew, is absolutely vital. Cockpit interruptions are frequent and distracting, but shouldn’t circumvent crucial checklists. If the flow of a checklist breaks down for any reason, there is a strong case to go back to the beginning and start it again. And then, don’t stow the checklist, move the marker or flip the page until the checklist is absolutely completed. Even if flying solo,
As for flying an aircraft with suspect instrument indications, the first thing is to consider whether the attitude and thrust setting
The investigators did not find any great mystery in the loss of Northwest 6231. A simple oversight here and a misinterpretation there led to the catastrophic loss of an essentially serviceable Boeing 727 and its precious crew. Regardless of the size of the aircraft or the experience of the crew, the operation of any
That cold night over New York the unfortunate crew saw events unfold at a rate that exceeded the ability to