Accident Probe: Twin Training

There’s a right and a wrong way to do anything, including communication with your instructor.

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When I first started training to fly multi-engine airplanes, it was solemnly explained to me that there were a few things the CFI and weren’t going to do. Yes, we were going to do stalls, but only from 5000 feet AGL or more. They all would be straight-ahead and power-off to the pre-stall buffet, followed by the published stall recovery procedure. Generally, that involved pitching the nose down to regain airspeed and control. Only as we accelerated above the red line (VMCA) with the nose down did we bring up power to both engines. The CFI would arrange his knees and hands so that the yoke couldn’t rotate past 20 or so degrees, limiting possible bank angles but poised to take over if needed.

Why the precautions? In part because piston twins aren’t certified for spins. In part because they have a greater tendency to enter unrecoverable spins after a stall break than a piston single. And in part because that record is especially unfortunate since a lot of the fatal unrecoverable spins in piston twins have involved training.

Some years ago, the industry took steps to help minimize what was considered an unacceptable fatal accident rate in piston twins. Among the policy changes was new guidance on stalling multi-engine airplanes. The sidebar (“The FAA On Stalling Multi-Engine Airplanes”) below summarizes current FAA thinking.

We’ll never know how many piston twins were spun—deliberately or inadvertently—but we do know the outcome for several. A quick-and-dirty search of the NTSB database for piston twins and the key word “spin” pulled up 32 entries between January 1, 2005, and December 31, 2014. All but one involved fatalities.

The important part about my multi-engine instructor sitting me down and explaining what we were going to do is a fundamental component of flight instruction. Briefing the lesson plan and getting buy-in from both sides of the cockpit is part of the deal. If either side has a concern, it should receive a fair hearing and a mutual solution. But you have to speak up.

Background

On March 4, 2017, at about 1330 Eastern time, a Beech B60 Duke was destroyed by impact and a post-crash fire following an uncontrolled descent in Duette, Fla. The private pilot and the flight instructor were fatally injured. The airplane had just been purchased by the pilot, and he was working with the instructor to meet insurance requirements. Visual conditions prevailed.

The flight departed the Sarasota-Bradenton (Fla.) International Airport (SRQ) about 1240. Radar data showed an overlapping track of left and right 360-degree figure-eight turns consistent with airwork. Radar data from the last 30 seconds of the flight depicted the airplane traveling northwest at about 1000 feet AGL and 104 knots groundspeed.

Investigation

Numerous witnesses agree the airplane was flying straight and level at a relatively low altitude when it departed controlled flight and entered a spiraling descent. Engine sounds were consistent throughout, with evidence of last-moment application of full throttle. Radar data showed the airplane maneuvering at between 1000 and 1200 feet AGL just before the accident.

All major components were accounted for at the accident site. Flight control continuity was confirmed from the control surfaces to the cockpit area. The flaps and landing gear were retracted. The trim actuators were within normal operating range. The three propeller blades from each engine were found separated from their respective hubs in impact craters. All blades exhibited similar bending and cambered-side polishing.

The private pilot held ratings for airplane single- and multi-engine land; he did not possess an instrument rating. On an insurance application two months earlier, the pilot declared 1120 total flight hours, including 800 hours in multi-engine airplanes, and 200 in the accident airplane make and model. The flight instructor had accrued 20,900 total hours of flight experience, with 165 hours make and model.

The private pilot spoke with three friends—two of whom were pilots—the evening before the accident, after his first day of training with the instructor. In those conversations, he described what he considered unsafe actions by the instructor, including one that resulted in the Duke entering a spin.

According to the NTSB, “as the pilot was using the standard technique of lowering the nose to recover from the stall, the instructor had advanced the power levers, and the airplane had entered ‘a spin.’” The airplane was recovered at about 2000 feet AGL. The NTSB said, “Both the pilot and the instructor were surprised and frightened by this event, and they landed soon afterward.”

Probable Cause

The NTSB determined the probable cause(s) of this accident to include: “The pilots’ decision to perform flight training maneuvers at low airspeed at an altitude that was insufficient for stall recovery. Contributing to the accident was the flight instructor’s inappropriate use of non-standard stall recovery techniques.”

There’s a lot going on here. On one hand, the private pilot had more make-and-model time than the instructor. He also had expressed his concerns about the instructor to three friends after the previous day’s flying, but there’s no record of his discussing them with the instructor. The outcome would indicate otherwise.

Meanwhile, the NTSB had this to say about the instructor: “Most critically, the instructor used two techniques that introduced unnecessary risk: increasing power before reducing the angle of attack during a stall recovery and introducing asymmetric power while recovering from a stall in a multi-engine airplane; both techniques are dangerous errors because they can lead to an airplane entering a spin.”

The NTSB clearly places the responsibility on the pilot in command: “The procedures performed contradicted standard practice and Federal Aviation Administration guidance; yet, despite the pilot’s experience in multi-engine airplanes and in the accident airplane make and model, he chose to continue the second day of training with the instructor instead of seeking a replacement to complete the insurance check out.”

A lot of factors can combine for us to find a mismatched training situation tolerable, even when it’s against our best instincts. But accomplished pilots receiving training have no obligation to defer to a more experienced instructor in the face of justified concerns.


The FAA On Stalling Multi-Engine Airplanes

The FAA’s Airplane Flying Handbook has these basic points to make about stalling twins:

  • Stalls with asymmetric power settings should not be attempted due to the likelihood of departing controlled flight and spinning.
  • Multi-engine stalls should be practiced from an altitude allowing recovery no lower than 3000 feet AGL, or higher per the AFM/POH.
  • No multi-engine airplane is approved for deliberate spins, and their spin recovery characteristics are generally very poor.
  • Spin awareness should be at its greatest during VMC demonstrations, stall practice or any condition of high asymmetrical thrust. Single-engine stalls are not part of any multi-engine training curriculum.

The FAA’s Flight Instructor Airplane Practical Test Standards states, in part, that “stalls must not be performed with one engine at reduced power or inoperative and the other engine developing effective power.


Aircraft Profile: Beechcraft Model B60 Duke

Engines: Lycoming TIO-540-E1C4

Empty Weight: 4425 lbs.

Maximum Gross Takeoff Weight: 6775 lbs.

Typical Cruise Speed: 230 KTAS

Standard Fuel Capacity: 142 gal.

Service Ceiling: 30,000 feet

Range: 1010 NM

VSO: 73 KIAS


Jeb Burnside is the editor-in-chief of Aviation Safety magazine. He’s an airline transport pilot who owns a Beechcraft Debonair, plus the expensive half of an Aeronca 7CCM Champ.


This article originally appeared in the March 2019 issue of Aviation Safety magazine.

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2 COMMENTS

  1. As an MEI I recommend to strictly adhere to safety recommendations. Not all MEIs do. I lost two friends while they were instructing in twins. Twins are not forgiving.
    A flight instructor who kills his student is a murderer!

  2. It was, and is, common practice in 14 CFR 25 certified jets to add full power at the first indication of stall. This CFI had over 20,000 hrs time, and although the article does not give his background, most pilots that have that experience also have many, many visits to high-level simulator training sessions for jet aircraft. Until recent years, repetitive airwork sequences involved approaching a full stall, and then powering out of it with ZERO loss of altitude! This deeply ingrained practice has no place in piston twin training! every application of power (at a high angle of attack) is an application of asymmetric power when both props are turning the same direction.