No matter what and where we fly, our speed usually is of interest. Sometimes, were just out loafing, watching the clouds above us and the cars below us. Other times, were trying to get somewhere and for any number of reasons want to do it as quickly as possible. In fact, a personal airplane often is an ideal traveling tool, one ensuring the fastest door-to-door travel times this side of a Star Trek transporter beam. Speed usually is a good thing. Of course, just as too little of that good thing can result in a stall, too much of it can result in structural failure. In many popular airplanes, achieving a speed risking structural failure can be a lot of work, involving a climb to several thousand feet of altitude, maintaining full power and deliberately pushing the nose over. This presumes, of course, the aircraft remains under control at all times. If it isnt under control due to distraction, for instance, or some other calamity, all bets are off. With other aircraft-aerodynamically clean high-performance pistons come to mind-its rather easy to see airspeeds well into the yellow arc: Just let your attention wander to a troublesome passenger for a few moments, or turn around to find the chart you misplaced in the back seat. Distractions, of course, occur all the time in the cockpit. Few of us would allow our aircrafts speed to get far enough out of control that structural failure is a risk. Sometimes, though, we intentionally push the speed limits. Reasons for doing so can involve being behind schedule or attempting to comply with ATC instructions. Neither is a good reason to push an aircrafts structural limitations, though. Background On April 11, 2009, at about 1054 Pacific time, a Piper PA-24-250 Comanche experienced an in-flight breakup during an uncontrolled descent in instrument conditions near San Diego, Calif. The airplane was destroyed during the breakup sequence and post-impact ground fire. An instrument-rated private pilot owned and operated the airplane, and he and his passenger were killed. The personal flight was performed on an IFR flight plan, having originated from the Whiteman Airport, Los Angeles, Calif., about 1004, in VMC. While en route, the pilot cruised at 7000 feet msl and transitioned to IMC approaching San Diego. At 1050:34, the pilot informed ATC he was descending to 4000 feet. At about 1053:04, the controller instructed the pilot to “descend and maintain two thousand six hundred keep your speed up.” Five seconds later, at 1053:09, the pilot responded “two thous.” The remainder of the pilots transmission was either interrupted or not recorded by ATC. There were no further communications with the Comanche. Investigation The airplane wreckage was located on a hillside about 5.5 miles east-northeast of the Miramar Marine Corps Air Station, and about 900 feet north-northwest (329 degrees magnetic) from the airplanes last recorded radar position. The magnetic bearing and distance between the initial point of impact crater and the cockpit was about 167 degrees and 50 feet. The majority of the wreckage was found scattered over a 150-foot-wide by 530-foot-long southeasterly path. All of the flight control surfaces were found in the wreckage area. Examination revealed the airplanes wing spars were bent and fractured in an upward direction. The separated outer wing sections were found several hundred feet away from the main wreckage and were not damaged by fire. The inboard wing spans, the vertical stabilizer with attached rudder and the left stabilator were found attached to the fuselage and were fire-damaged. The right stabilator was found separated from the empennage, and its airframe attachment structure was observed bent in an aft direction. The leading edge of the stabilator was crushed in an aft direction and bore witness marks consistent with the deformation pattern from a separated right wing skin component. Recorded radar indicates the airplanes altitude was 4200 feet about two seconds before the pilots last transmission, at 1053:09. At 1053:11, the airplane was at 3800 feet; at 1053:16, the airplane was at 3300 feet. The airplanes average descent rate during this nine-second interval was about 6000 fpm, and the southbound airplanes course was changing in a clockwise direction. By 1053:16, the airplane was on a westerly course, and there were no further recorded radar hits. The closest aviation weather observation station site was the Miramar Marine Corps Air Station, about 5.7 miles west-southwest from the accident site. At 1055, Miramar (elevation 478 feet msl) reported broken clouds at 2500 and 3100 feet, with an overcast at 4800 feet agl. The wind was from 210 degrees at five knots, and the visibility was 10 miles. The temperature and dew point were 13 and 9 degrees Celsius, respectively. According to family members, the pilot was familiar with the route, having flown it on several occasions. Probable Cause The NTSB determined the probable cause of this accident to include the “pilots failure to maintain control during an en route cruise descent through multiple cloud layers, resulting in an in-flight breakup.” Which leaves little with which we can argue. However, one thing missing from the accident report-and which is usually available when good radar data is retrieved-is the airplanes groundspeed. Having that information would help establish if the pilot had allowed airspeed to build to near redline before the breakup sequence began. Without it, an obvious conclusion is a few moments inattentiveness by the pilot allowed the airplane to get away from him, perhaps enter a steep spiral to the right and the wings came off. But another conclusion is the ATC request to “keep your speed up” may have played a role. Especially when flying a relatively fast airplane like a Comanche, pilots often are happy to show off a bit. This is even more true when heading into a major airport where theyll be mixing with “the big boys.” Putting the nose down to pick up speed is one thing; pushing the airplanes limitations is another. But demanding too much of our aircraft seldom works out well unless, as the old joke goes, “further flights in that airplane appear unlikely.” By trying to hard to impress ATC or comply with a request, were letting a controller fly the airplane for us. As this accident should demonstrate, thats a bad idea.
