My latest blog failed to discuss one of the worst small plane accidents that recently occurred. On February 16 at 1130 hours a 1960 Beech Debonair N400DJ took off from Telluride (KTEX) at around 1130 hours. Weather was light snow with visibility 1 mile, the average temp about 38F.
The reason I’m writing about this sad event is that there are some important factors to discuss, such as the negative effects of altitude on aircraft performance. There were no survivors in this crash, all three experienced aviators died at the scene.
The main effect of altitude is the decrease in air density as the altitude increases. The principle effect on the typical internal combustion engine is to decrease engine power output with increasing altitude. ( Reference from Airliners.net) Also the true airspeed of a stall increases at the rate of 2%/1000 feet. The indicated stall speed however remains unchanged. Very importantly, the rate of climb for a given airspeed decreases with altitude. This is what concerned me about this crash. The question being: could N400DJ climb fast enough to get around or over the surrounding terrain?
We may never know what brought these intrepid aviators down. I await the official NTSB report. I would have to wonder about engine performance and possible problems in that area.
In doing my reading, I also learned something about turboprops and jets and their problems with altitude. Apparently turboprops run into problems because of propeller efficiency and some jet types with their wing aerodynamics.
Before I sign off, I’ll tell you about a trip I made as a young and budding pilot in a Cessna 172 between Syracuse, NY (SYR) and Boston, MA (BOS). There were three fellow med students and I trying to go for a weekend break. Weather forecast so-so, VFR with clouds and minimal precip enroute. Temperatures were above freezing. Shortly after leaving SYR however, clouds started to appear. Scattered and low at first but as we kept going the cloud cover increased. As I was only VFR qualified, although I had some IFR training, I climbed above the clouds until I couldn’t get any higher. This was about 15,500 feet with no Oxygen aboard. We must have been in good shape as none of us passed out. Ouch! The airplane performance notably kept getting worse as we climbed higher. It felt light and a bit unstable. (Maybe some of that was due to light hypoxia on my part.) Finally when we got well past Albany (ALB) the clouds began to lessen. There were breaks that allowed us to see the ground, and as we passed Worcester, we could see Boston in the distance. All I can say is that we made it, and were damn lucky and awfully glad to put our feet on the ground when we landed.
So be aware of the limitations that may impact on your plane at higher altitudes. Check your flight manuals for performance data that applies.
Happy flying fellow pilots. May you fly high, fast and upright.