Bits and Pieces
First Flight in My New Homebuilt – Debrief
By Jack Dueck, EAA Canadian Representative, Homebuilders Advisory CouncilThe first step after every test flight involves a thorough debriefing of any and all aspects of the flight. Let’s go over some of the issues and concerns that have been experienced on first flights.
Engine: As soon as practical and in a sheltered space (preferably a well-lit hangar), remove the engine cowlings and check over the entire engine installation. Has oil accumulated on the inside of the cowling? Can it be traced to a specific point of origin?
Visual check with cowl off
On the first flight of my RV-4, engine oil collected in the front lower cowling. On tracing it to its source, we discovered that the front main oil seal was missing, presumably never having been installed at the time of major overhaul by the engine rebuilder. The first flight of my wife Jean’s RV-9A was shortened because traces of oil appeared on the windscreen. We traced this oil leak from oil on the upper cowling coming from the breather tube relief vent.
Check the cowling and baffles for any signs of chaffing. The engine will move an amazing 3/4 inch during taxiing and flight.
Check wiring harnesses for anchorage and tightness. Is there any unusual discolouration in the exhaust piping that would indicate leakage? Also, pay attention to primer lines and fuel system components. Engine vibration on one of our early flights resulted in a broken primer fitting at the cylinder inlet port.
While performing the first flight on a newly built RV-7A, engine temperatures ran above acceptable limits, and the flight had to be cut short. Baffles and the oil cooler were the suspected culprits, and some rework in these areas helped to resolve the problem for subsequent flights.
Instrumentation: On the RV-9A, both the manifold pressure gauge and the tachometer proved unreliable and had to have their sensors replaced.
Radios and radio communications are often compromised, and although they seem to work perfectly normal on the ground, as the aircraft becomes airborne with increased noise surrounding the pilot, communication becomes more problematic. Feedback, squelch, and antennae placement all play pivotal roles.
Vibration: On the initial test flight on our Luscombe some years ago, the engine developed a substantial vibration immediately after takeoff. We rechecked the propeller tracking, the engine mounts, etc., and finally found that the engine mount-to-firewall bolts, although snug to torque values, needed to have additional tightening to solve the problem.
Control systems: On the initial high-speed taxi on another RV with a constant-speed propeller, the engine governor allowed the prop to overspeed. In fact the tach reading exceeded 3,000 rpm before the prop control reduced the prop rpm to an acceptable level. Obviously this occurred while still on the ground, and corrective action could be taken without danger to the flight.
Flight control systems: Without exception, the evaluation of the flight control systems is a paramount factor in the safety of the first flight. We have all heard of the case of the ailerons being hooked up in reverse action. During our preflight check, do we look to see if the control stick or yoke simply moves the ailerons, or do we look to see if the left aileron comes up when we move the controls to the left?
After the first flight, does the movement of any of the controls produce a scraping or the feeling of any resistance to the movement? If any of the controls produce any feeling other than a clean, noiseless movement, investigate and resolve the situation. Some years ago at EAA AirVenture Oshkosh, the owner of a tube and fabric homebuilt requested his aircraft be judged. The judging chairman came to our Technical Counselors’ Headquarters and instructed us to check out the interference in the aileron movement. The aircraft ended up being grounded until remedial work was done to correct a potentially dangerous situation. I don’t think this owner won a “Lindy”!
One of the most potentially dangerous control malfunctions that can be encountered, I believe, would be a failure of the flap control mechanism giving the aircraft a differential flap extension. I pay a great deal of attention to the flap control system, checking for soundness, excessive play, or any anomaly that could create a problem.
Ground handling: During this first flight, was there any discernible problem associated with the ground handling of the aircraft? On the proposed first flight of our Luscombe, I encountered my only great scare in first flights. I intended to perform a high-speed taxi test prior to lifting off, so I communicated my intentions to the control tower, which then requested that I perform my taxi test and first flight from an alternate (shorter albeit unused) runway.
This turned out to be a wise decision by the controller. I applied power smoothly and allowed the tail to come up. I was cognizant of my expected liftoff speed and remained comfortably below this number to avoid any unexpected premature flight. The aircraft tracked okay and showed no problem…until I cut the power to allow the tail to return to the runway! With the slipstream airflow and rudder authority removed, or at least greatly reduced, this aircraft became a monster. It veered sharply to my left, the right wing dropped, and the tip scraped the runway; only with a hard application of right wheel braking could I prevent an unexpected and instantaneous 360-degree view of my world. The culprit was excessive toe-in on the right landing gear.
Flight testing involves the heightened and active use of our various senses to anticipate and react to any unexpected occurrence. Consequently, you don’t want to overload your capability to react to and control any unwanted situation. Go from slow to fast; from high to low, from known to unknown, all carefully and selectively. Carefully acknowledge any snags, problems, or even only concerns, and resolve, repair or replace, fix, and correct every one of these issues before the next flight. The next flight then will serve to confirm any corrective action taken, and then if all systems are go, expand the flight test envelope to the next incremental stage.Time for that celebratory refreshment!