If your primary training experience was like mine, my instructor and I spent a lot of time coaxing a tired trainer up to altitude, only to come right back down. Much of the time, it was-hot-south-Georgia-in-the-summertime hot-and the little 150 in which I sweated out my private did okay, all things considered. It was pretty far removed from being a homesick angel, however.
Spins werent in the curriculum then, but we did a bunch of stalls and slow flight. After each abrupt descent, we again explored the 150s best climb rate configuration and engine cooling capability. Of course, a 150 doesnt lose that much altitude in a stall, even if aggravated by a sweaty student pilot, himself perhaps aggravated. But, we still took the time to get at least 3000 feet between us and anything hard. Thankfully, we never came close to needing all that room.
Since then, as I checked out in larger, faster and heavier airplanes-and obtained spin training-Ive taken to wanting even more air beneath me before slow-flight or stalls. The issue, of course, is what happens if the airplane enters an inadvertent spin or I screw up the stall recovery. Better to be safe (have too much altitude) than sorry (have not enough).
As we will see this month, as airplane weight, performance and complexity increase, so should your minimum altitude for stalls and slow-speed work. This is especially true when neither the pilot receiving instruction nor the instructor are all that familiar with the airplane.
Background
On December 27, 2006, at 1426 Eastern time, a Mooney M20F collided with trees and terrain following a loss of control during a local flight over Mt. Gilead, Ohio. The airline transport rated pilot-in-command (PIC) and the certified flight instructor (CFI) on board were both fatally injured. The airplane was substantially damaged. The training flight was operating in visual conditions, having originated from the Knox County Airport (4I3) in Mt. Vernon, Ohio, about 1245.
The PIC, who was a recently retired airline pilot with 16,700 hours, purchased the airplane on December 11, 2006, and was obtaining familiarization training for insurance purposes. The accident occurred during his first flight in the airplane. The CFI had more than 5500 hours experience, of which 212 hours were in Mooney M20 airplanes. There was no indication the PIC and CFI had flown with each other prior to the accident flight.
The airplane was involved in a propeller-stoppage event earlier in 2006. In the aftermath, the engine was overhauled, a new propeller was installed and the airplane received an annual inspection. It had flown approximately 17.1 hours since being returned to service in October 2006.
Witnesses reported an uneventful departure and, almost two hours later, seeing and hearing the airplane flying from the east to the west. One stated, “It looked like it went straight up, or tried to, then I saw it just go straight down.” Another said the engine seemed to be working and that it was loud. The witnesses reported seeing the airplane coming “straight down” nose-first until it descended into the trees. Another witness reported seeing the airplane “twist” a little prior to its final descent.
Investigation
A weather observation 13 miles northwest of the accident site at 1452 included wind from 260 degrees at eight knots, visibility 10 sm and few clouds at 10,000 feet. Terrain elevation at the accident site was 613 feet.
The airplane contacted the terrain in a nose-down attitude. The attitude indicator was jammed in an approximate 30-degree nose-down, 45-degree left-bank attitude. The landing gear and the gear handle were in the down position. The flap-handle position could not be determined, but both wings flap hinges were in the extended position. The left wing was approximately three-quarters full of fuel. The propeller spinner exhibited rotational twisting and scoring. All three propeller blades displayed signs of power being developed at impact, including chordwise scratches. No pre-existing mechanical failure/malfunction of the engine was noted which would have precluded normal operation.
The NTSB reviewed radar data, which showed changes in heading, altitude and groundspeed during the last 26 minutes before the crash. During that time, the airplanes altitude varied between 4500 feet and 2500 feet msl while its groundspeed was as high as 164 knots and as low as 39 knots. At 1423, the altitude and groundspeed decreased. Just prior to the loss of radar contact, the airplane was at 2500 feet msl with a ground speed of approximately 57 knots.
Probable Cause
The NTSB determined the probable cause(s) of this accident to include: “Both the pilot-in-command/aircraft owner and the flight instructor failed to recover from the stall and the flight instructors inadequate supervision of the flight.”
One of three things happened in that Mooney. One, the two experienced pilots simply failed to realize how low they were or thought they needed only 1887 feet of altitude (2500 feet msl less the terrain elevation of 613 feet) to recover from a stall. Two, there was disagreement about who was flying the plane, with the end result being “no one.” Three, someone froze at the controls, or one pilot fought the other for control during the stall recovery, preventing it. Well never know for sure.
What we do know, however, is 1900 feet isnt enough to recover a high-performance single in its landing configuration from a fully developed stall. Witnesses didnt report seeing a spin. Their recollections along with evidence at the scene indicate the engine was at a high power setting.
Why so low? After a series of stalls and slow flight, the pilots probably didnt realize how low they were. It was a high-workload cockpit. They probably werent paying much attention to the altimeter, preferring instead to look outside for traffic and fly the airplane visually. Also, they probably didnt realize how much altitude they had lost in earlier maneuvers. The record shows a considerable amount of time spent doing air work; this might have been the last stall of the flight, with pattern work to follow, so why bother gaining more altitude?
Air work is a very necessary part of our flying, but it comes with increased risk. One way to minimize that risk is to ensure you have adequate altitude before intentionally entering a fully developed stall.
