Ever wonder what the job of a helicopter manufacturer’s production test pilot is like or what the helicopter goes through to get its airworthiness certificate? Many of us take for granted that when the helicopter leaves the factory all its components have been manufactured and installed correctly. It’s the production flight test pilot and a flight test mechanic that put their butts in the helicopter for that first flight to begin a series of flight tests that eventually leads to an airworthiness certificate.
After the helicopter has been “built” it is moved into an area of the factory Robinson calls “Flight Test”. Here, the main rotor and tail rotor blades are installed and rigged. The helicopter is hung from the main rotor hub, weighted and the empty weight center of gravity and moment calculated. After completion of a 25-page inspection checklist by a designated Inspector, the ship is ready to fly. A production test pilot and mechanic are assigned to take the aircraft through the production flight test procedures specified by Robinson Process Specification-62 (RPS). Production test flying is a unique job and quite a learning experience. I think I learned more about what makes a helicopter tick in my first year of production test flying than I had the 10 previous years. To be hired as a production test pilot Robinson requires at least 1500 Robinson flight hours and most seem to stick around for quite a while. Unlike many flying jobs, it’s a Monday through Friday schedule, the pay is good and the health/retirement benefits are at the top end of the spectrum.
The first item RPS-62 requires is to conduct an extended ground run to check various systems, such as the low RPM warning system, clutch engagement system and the governor. The tail rotor is tracked and balanced and the fan balanced. The first flight is to track and balance the main rotor which may take two or three flights depending on the blade match. It’s quite a thrill to get a brand-new helicopter light on the skids then slowly lift it up to a hover for its very first flight. The test pilot and mechanic conduct test flights at three different loading conditions and each condition may require two or three flights to get everything dialed in. First, a flight at maximum gross weight and at a neutral center of gravity is used to check a number of items such as, throttle correlation, control forces and vibration levels in different phases of flight. Tail rotor controllability is checked while climbing at 50 KIAS, takeoff power and the pilot applies left pedal to produce a 30º left yaw followed by a 30º right yaw in autorotation at 50 KIAS and 90% rotor RPM. The second flight condition is at the aft center-of-gravity limit. A 40 lb. weight bag is attached to the tailcone to move the C of G to the aft limit. Flying at Vne, the test pilot will apply cyclic to the forward cyclic stop checking for at least ¾ inch movement which insures proper forward cyclic rigging. The helicopter’s proper autorotational RPM is also checked on the aft C of G flight (If not on this flight on a separate flight). From the autorotational RPM chart found in the maintenance manual the design rotor speed is compared to the observed rotor speed in autorotation at 50 KIAS with the collective full down. The speed must agree within 1%. If not, both pitch links must be adjusted to change the minimum collective pitch of the rotor. The last flight is accomplished at the forward center-of-gravity limit. Weight is attached to the toes of each skid to move the C of G to the forward limit. From a slightly higher than normal hover altitude the test pilot will move into rearward flight and accelerate to stabilized rearward flight at 17 KIAS (estimated by the pilot). The cyclic is moved to the aft control stop and at least ¾ inch movement insures proper aft cyclic rigging. Today, with so much optional equipment and avionics choices that can be selected by the owner, all installed options from an autopilot to the heated seats in the R66 are tested for functionality during the three production test flights.
The “safety buy-off”, which shows all safety related flight test items have been successfully completed and “final acceptance” may only be conducted by an FAA approved acceptance test pilot. Completion of all the production flight tests normally takes between four to six flight hours but can take longer if problems are encountered. I recall one ship where just about the entire rotor system: blades, hub, swashplate had to be replaced to get everything flying together nicely. The next step in the process is the Conformity Inspection conducted by a DMIR (Designated Manufacturing Inspection Representative), a Robinson employee who is designated by the FAA to conduct the inspection. He insures the aircraft conforms to the type design with respect to all drawings and specifications. The DMIR will then sign and date the Standard Airworthiness Certificate. This date is, essentially, the helicopter’s birthday since it becomes the Date of Manufacture and now the clock begins for the aircraft’s annual inspection schedule and the 12-year overhaul. After the aircraft receives its Standard Airworthiness Certificate it is moved to the Delivery Center (or shipping department if it is going overseas) to await one of the more important steps in the process: final payment.
Tim Tucker
December 2018