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Limited Effectiveness of Flight Simulators in Stall Training

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Crash site at Teterboro Airport. Photo credit: News 4 NY

In a well publicized Loss of Control In-flight (LOC-I) accident on May 15, 2017, a Lear 35 crashed while on a circling approach at Teterboro Airport in New Jersey. While many of the specifics of the accident appear relatively clear, accident investigations have a way of bringing up information which might never have been guessed at face value.

NTSB on Teterboro Lear 35 Crash

Just over a week ago, the NTSB put out a News Release explaining that while the preliminary investigation is still underway, the details that are being analyzed are now available to the public. This link to their docket of information comprises the evidence that the NTSB is evaluating regarding the accident.The qualification history and deficiencies of both the captain and second-in-command (SIC) are both shocking and shameful. That information will no doubt gather the most hype in both general and aviation media, and because of that there is an underlying story that will likely be missed, even if its ramifications are much more broad.
The supposition that the accident involved a stall has been confirmed by both the Captain’s statement of “stall” on the cockpit voice recorder, along with the SIC’s verification with the simple, yet ineffective word “yup”. The strain overheard in the captain’s voice, along with the maneuvering required by the approach indicates that the stall encountered was accelerated (occurred with an acceleration above 1 G) and most likely involved a skidding condition to try and improve the airplane’s turn rate to align with the landing runway.

Unique Flavor of Many LOC-I Stalls

These types of stalls in the traffic pattern are not unusual. In fact, they are classic; they are one of the most common types of LOC-I accident. What is less standard is the fact that this occurred in a jet. These types of stalls are much more common in light single-engined aircraft. There are many reasons for this, such as the fact that jet pilots typically have more experience and are required by regulation to undergo regular training. Jets often have warning or protective features that light aircraft do not, and almost always have greater excess energy for recovery.
One thing that is the same about stalls in smaller propeller aircraft and jets is the aerodynamics of the stall. When the angle between the relative wind and the wing chord line, the angle of attack, becomes too great the airflow is going to separate and lift will be lost.

Simulators to the Rescue?

Interestingly, despite the amazing complexity and sophistication of today’s modern flight simulators, simulating the full aerodynamic stall realistically has not been a requirement for their certification. That was because the simulator was designed and built for training, and in the past, that training and associated evaluation of pilots did not require anything beyond the first indication of a stall, which includes the stall warning. Certification requirements require the stall warning (there are several methods of aural, visual, and tactile warnings employed in different aircraft) to occur a set amount prior to the actual stall, so the simulator itself was never required to fully replicate a stall.
This would be no problem if the behavior at the first indication of the stall was the same that pilots experience when an actual stall occurs. Unfortunately, it is not, and the differences can be extremely startling for pilots encountering some of the characteristics of a stall which they are not familiar with from simulator training alone. For some pilots, that will be changing soon.

APS Stall Instruction
APS Stall Instruction

Extended Envelope Simulator Limitations

Beginning in March of next year, all U.S. airlines (Part 121 Air Carriers) will be required to train their pilots all the way to the full aerodynamic stall, with simulators being able to accurately model the aircraft’s behavior to 10 degrees beyond the stalling (critical) angle of attack. Accommodations are being made for deviations to this requirement for certain aircraft which do not have adequate means of simulation. This is certainly an improvement, but extended envelope simulators will still not be able to accurately replicate more dynamic stalling conditions, or stalls with sideslip present (slipping and skidding stalls). Only an aircraft can illustrate these aerodynamic conditions, along with the human factors related to the actual recovery from aggravated stalls experienced in flight.

Accurately Addressing Full Stall Training

This regulation will enhance training related to stalls, but only extends to those pilots involved in airline flying. For others, such as the pilots in the Lear 35 accident at Teterboro, the first time they may be exposed to the full range of aerodynamic characteristics associated with a full aerodynamic stall may be when they see it in real life. That may be too late, as it was for the Lear 35 crew at Teterboro last year.
There is an alternative.
Proper Upset Prevention and Recovery Training (UPRT) provides a holistic understanding of the factors affecting a stall, along with on-aircraft training which highlights the characteristics of a stall that all fixed-wing aircraft are susceptible to. An all-attitude-capable, spins-approved aircraft with adequate margins for spin recovery can illustrate the escalating patterns of a developing aircraft upset event, as well as the safe practice of recovery if an upset is not prevented. For pilots who want to ensure they have the skills necessary to avoid or recover from situations such as those described by the NTSB this week, comprehensive UPRT provides the best way to mitigate the LOC-I risk, the number one cause of aviation fatalities. This has been, and is, APS’ full-time focus for three decades: APS Upset Prevention & Recovery Training Programs


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