Testing Articles

In October we introduced non-maneuvering static longitudinal stability. Through examples we explained how the amount of force you must apply to the control stick or yoke to fly an airspeed different from your trimmed airspeed can affect the ease or difficulty of flying your airplane.

The August “Test Pilot” completed our discussion of flight path stability, which showed how to take the data gathered using the flight-test techniques described in the July “Test Pilot” and transform the raw test-day numbers into a meaningful plot. This flight path stability plot showed you how the example airplane’s final approach path angle varied when the airspeed changed.

In September’s "Test Pilot" we laid the foundation for climb performance testing. We related climb rate to excess power and showed that the maximum excess power occurs at an airspeed (VX) that is neither the maximum power-available nor the minimum power-required airspeed.

In May we discussed flight control system freeplay and centering. Building on April’s introduction to flying qualities we showed how you interface with the airplane through its flight controls, which can affect the ease or difficulty of piloting tasks, and we gave specific measurement techniques and some practical "normal" flying assessment suggestions.

In April’s "Test Pilot" we introduced flying qualities and described the concepts of stability and control from two perspectives-in terms of design goals and how they affect you when you’re flying your airplane. After integrating these number-based airplane characteristics with pilot opinion, we called the result handling qualities, the focus of which is how your airplane feels to you when performing piloting tasks.

Using the range and endurance testing described in the February “Test Pilot,” in March we explained level flight performance data reduction that produces useful tables and plots of speeds that result in an airplane’s maximum range, endurance, and specific range.

Sometime after that memorable initial test flight, and before you fly your airplane again, check conditions inside the engine compartment. You can't be too careful at this early operational stage. Remove the cowling and look for fuel and oil leaks, loose clamps, wiring problems, and the security of all installed components.

The aircraft has been thoroughly checked, operated and taxied as described last month, and you know it is, mechanically, as near perfect as it will ever be. So, if all goes as planned, your homebuilt will, at last, fly for the very first time.

Many builders have the mistaken notion that flight testing an amateur-built aircraft must take place immediately after the FAA certification inspection and that it consists merely of that legendary first flight. Most are aware, however, that the homebuilt will have to fly oft its 25 hour quarantine in an approved flight test area. The minimum is 40 hours for homebuilts with uncertificated engines or propellers.

I JUST LOST a friend. He was making that long awaited first test flight in his brand-spanking-new homebuilt. As is the case with most aircraft accidents, we don't know the officially determined cause . . . may never hear what that is. Only this much was relayed to me. "He took off and was climbin', when suddenly it nosed down and went straight in."Physical incapacitation? Possible.