Test Flying: Operational Check Flight

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operational check flights

Test Flying: Operational Check Flight (OCF)
In related articles we talked about test flying your homebuilt aircraft on its first flight. In this post we’ll discuss flight test of certified aircraft, both from a regulatory and a practical standpoint.

“By failing to prepare, you are preparing to fail.”
― Benjamin Franklin

The Regulations

91.407 (b) — Operation after maintenance, preventive maintenance, rebuilding, or alteration.

(a) No person may operate any aircraft that has undergone maintenance, preventive maintenance, rebuilding, or alteration unless—


make a test plan

(1) It has been approved for return to service by a person authorized under §43.7 of this chapter; and

(2) The maintenance record entry required by §43.9 or §43.11, as applicable, of this chapter has been made.

(b) No person may carry any person (other than crewmembers) in an aircraft that has been maintained, rebuilt, or altered in a manner that may have appreciably changed its flight characteristics or substantially affected its operation in flight until an appropriately rated pilot with at least a private pilot certificate flies the aircraft, makes an operational check of the maintenance performed or alteration made, and logs the flight in the aircraft records.

(c) The aircraft does not have to be flown as required by paragraph (b) of this section if, prior to flight, ground tests, inspection, or both show conclusively that the maintenance, preventive maintenance, rebuilding, or alteration has not appreciably changed the flight characteristics or substantially affected the flight operation of the aircraft.

No that we all have read the regulation, what does it mean?

Common sense – if something has been repaired that can even remotely cause a problem if it isn’t working properly or if it could have been mis-installed or if something unrelated was removed and reinstalled and it could cause problems, it needs a test flight.

Hopefully, if you are reading this article, this question will make it clear: Would you put your family in the airplane and take off across the mountains before test flying it? If this answer is “no” an OCF is in order.

preflight inspection

Practical Advice for your OCF
The regulation sets the requirement, but doesn’t tell you how to do it or offer any suggestions that could help keep you safe.

THE PILOT – Are you current and proficient? If not, you might seek out someone who is to do the test flight or make arrangements to get yourself back up to speed. This is a common problem; if you own the airplane and it has been down for major repairs, chances are you haven’t flown. The last thing you want to do test fly an aircraft when you aren’t on your game.

THE ENVIRONMENT – Again common sense, but let’s not test fly the airplane in poor weather. You don’t want to find out you have a serious rigging issue when there’s a 30 knot  crosswind. Nor do you want to try to break-in a new engine when it’s rough and you can’t keep the power up. Pick conditions that are ideal and stick to your plan. Also some airports are less than ideal, you might consider taking off from where the airplane is located and flying to a larger airport for the landing depending on what it is you are testing.

THE AIRCRAFT – We need to fully understand what it is we are testing. If the airplane had substantial repairs, this may be a long list. Don’t be surprised when you go out to test fly for one thing and find something unrelated isn’t working or is affected. Airplanes are a compilation of systems and those interrelationships aren’t always intuitive.

THE PROCEDURES – For more complex OCFs, I would recommend writing down exactly what you plan to do. It is too easy in the heat of battle to lose track of the plan. You don’t have to produce elaborate test cards, although that would be nice, but you need to have something. Some manufacturers publish procedures for certain types of operational check flights.

THE FLIGHT PLAN – Develop a detailed plan. I don’t recommend just going around the patch – remember, we plan to put our family in the airplane on the next flight. Figure out how high you are going to go. I would recommend staying close to an airport. What manuevers should you perform? Speed ranges? Power settings? The idea is to think through these things prior to jumping in the airplane.

THE PRE FLIGHT – If you have everything done and you and the airplane are ready to go then the focus has to be on the actual flight.

  • Know your emergency procedures. Certain emergencies dictate that you memorize the critical steps. This is not the time to be looking for that checklist stuffed behind the seat.
  • Sit in the aircraft and ‘dry fly’ every procedure, especially the emergency ones
  • Visualize your flight from start-up to shut-down
  • Don’t be afraid to pull the plug on the day of the flight if you are “feeling it”

THE FLIGHT – The execution of the actual flight should be easy compared to the effort spent planning – that’s the result you want.

aircraft checklist

Make sure you do your normal required items such as; performance calculations, weight and balance, and getting a briefing for weather and NOTAMs (especially TFRs).

The fuel load should be commensurate to your plan; don’t care too much, but make sure you leave yourself options.

Take notes during the flight. Depending on what you are testing this can be very important for later troubleshooting or for establishing baselines (rigging and new engines come to mind).

Minimize distractions. There have been terrible accidents caused by something minor that took the pilot away from the primary job of flying the airplane. Almost nothing in an airplane requires an immediate reaction. Get the airplane in a safe state and then work the problem.

by Brent

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