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Stage Two: Making The Initial Flight Test
By Tony Bingelis (originally published in EAA Sport Aviation, February 1989)
Today is the day!
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.
THE TEST FLIGHT SCENARIO
There are several different scenarios that could categorize a particular initial flight test.
The worst possible case scenario would be one featuring A LOW TIME BUILDER-PILOT with little or NO TAILDRAGGER EXPERIENCE who insists on testing his newly completed ORIGINAL DESIGN homebuilt which is fitted with a CONVERTED AUTO ENGINE and A HOMEMADE PROPELLER . . . and trying to do it from a SHORT DIRT STRIP on a WINDY DAY.
Here he is confronted with many unknowns - hoping that everything will work right and prove to be airworthy . . . all in a single test flight! This could prove to be very dangerous.
Obviously, he should minimize the risks by limiting the number of unknowns for the initial flight test. For one thing, at the very least (as explained last month), an experienced pilot should be allowed to perform the initial flight test.
How many other risk factors does he have control over?
Unfortunately, in the case of a new homebuilt equipped with a newly overhauled engine, or an unproven auto engine conversion, that increased risk factor has to be accepted.
At any rate, regardless of the number of unknowns to which any test flight will be subjected, the safest initial flight test will be one that is carefully thought out and planned before hand. The test flight must then be flown according to that plan . . . doing no more and no less than called for in the plan.
Develop your initial flight test plans along these lines:
I'm sure you tried to pick an ideal day for the flight. We all know that the best time to fly is during the early morning hours or late afternoon. That's when everybody makes their best landings.
The wind should be calm or light and down the runway. Although conditions are seldom ideal, don't be so eager to fly that you accept gusty or crosswind conditions for that most important first flight.
If the winds are gusty, high or quartering across the runway - postpone the flight until another time. Remind yourself that it took years of patient work to get to this point, so don't get impatient now.
EMERGENCY PLANS AND PROCEDURES
On the way to the airport, and after you get there, review your emergency plans, procedures and ground support needs.
- Know what your ground support will do and can do. Hopefully you did not invite a crowd. An initial flight test needs no such distraction or tension inducing atmosphere. This is not an air show. However, the first flight of a homebuilt, for most of us, is a once in a lifetime event and should be appropriately recorded on film. Try to get someone with a telephoto lens and/or a camcorder to do the honors.
- Emergencies do happen when least expected, so know what you are going to do IF:
- . . . . the engine quits soon after take-off.
- .. . . there's a fire on board and the cockpit fills with smoke.
- . . . the airplane is terribly wing heavy, tail heavy or nose heavy, and very hard to control.
- . . . . you lose communications with your crew, unicom, tower or chase plane (if you have one).
- . . . . the propeller throws a blade, or the spinner breaks.
- . . . . the throttle jams and cannot be moved.
- . . . . one of the controls jams, or a cable breaks.
- . . . . the engine temperatures rise rapidly and peg past the redline.
- . . . . oil splatters your windshield and the oil pressure begins to drop.
- . . . . your canopy latch fails and the canopy pops open.
- . . . . some part of the aircraft structure fails.
Obviously these are not the only things that can happen without warning on that first flight test, however, they are probably the most life threatening.
Prepare yourself mentally, before the flight, and review the options and logical corrective action you could take should one or more of the conditions occur.
Keep this essential thought in mind. You must, when airborne, regardless of the emergency that arises, CONTINUE TO FLY AND CONTROL THAT AIRPLANE! DON'T LET IT STALL. FLY IT ALL THE WAY TO THE GROUND IF YOU HAVE TO, BUT DON'T LET IT STALL.
Of course, it is unlikely that any of the conditions will befall you, but be prepared, and know what you would do (could do) if something unexpected did happen.
PERFORM A PREFLIGHT CHECK
You already know your airplane has been checked and rechecked (we covered all that last month), and is in perfect condition. But, remember, according to regulations you are still required to perform a preflight check before you fly it today. Make it a good preflight. Use a prepared preflight checklist - at least for this occasion. Here are some important items you should not overlook:
- The first, of course, is to see that the ignition switch is OFF, that the throttle is retarded and that the wheels are chocked.
- Pull the prop through five blades. This will assure you that:
- . . . . the engine has compression in all cylinders.
- . . . . the clicking noise you hear means that the magneto impulse coupler is working - and that portends a normal start.
- . . . . the inspection of the propeller blades and spinner will not be overlooked.
- Check your fuel and oil to see:
- . . . . that you have plenty of fuel for the flight, Don't rely completely on the fuel gages. Use a dipstick to check the fuel level visually against the fuel gage reading. Don't fill your tanks completely. About half the normal fuel capacity should suffice.
- . . . that there is no water present in your fuel sumps.
4. Clean your windshield, complete the other recommended walk-around preflight inspection items for your particular aircraft, and you will be ready to go.
NOTE: A crash helmet and parachute should be worn . . . all professional test pilots wear them. Some amateur test pilots wear a crash helmet but few bother with parachutes. Their rationale for that? The most critical phase of the test flight takes place at low altitude and a chute, they feel, most likely would be ineffective below a thousand feet of altitude anyway. Besides that, no structural testing is planned for that first flight. Now, the decision is yours to make.
Give last minute instructions to your standby crew. Start the engine.
1. Use your Pre-Start Checklist.
2. Immediately monitor your oil pressure. Check and set the other instruments.
3. Switch fuel tanks and run the engine on each tank. Set the fuel selector to the take-off tank.
Taxi to the take-off runway and hold position. Complete your pre-take-off cockpit check.
NOTE: A small 4 cylinder Continental or Lycoming aircraft engine, at full throttle, should yield at least 2,000 rpm, static, with a fixed pitch propeller. This minimum rpm requirement will at least assure you of sufficient power for the take-off . . . even if it doesn't prove to be the ideal cruise or climb propeller for that aircraft engine.
- Make your engine run-up as recommended by the engine manufacturer. Using your checklist:
- . . . . cycle the prop (if a controllable propeller is installed.)
- . . . make your magneto check. Be sure you return the ignition switch to the BOTH position. If you have been doing a lot of taxiing, or have been idling the engine for quite awhile, the spark plugs may have become a bit oil fouled and, consequently, your magneto drop could be a bit high. Run the engine briefly at a higher rpm and re-check the mags.
- . . . check the carburetor heat and other items on your checklist.
- . . . do not attempt a take-off if the cylinder head temperature (CHT) is near or at the limit. The engine could fail. If this occurs return to the ramp and correct the problem.
- If appropriate, turn on your electric fuel pump and deploy whatever amount of flaps is recommended for take-oft.
- Without further delay, clear the area (don't forget to look down the runway, too).
- Announce your intentions to the local traffic, or if appropriate, call the tower for clearance. Align the airplane with the runway centerline and start your take-off roll.
- Advance the throttle smoothly to FULL throttle. Glance at the tachometer to see that you are getting take-off rpm. If yours is a taildragger, keep the tailwheel firmly on the ground (with stick back pressure) until the rudder becomes effective (about 30 mph).
- If you are not airborne by mid-field, abort the flight.
- Allow the airplane to fly itself off.
- Don't pull it off. Guard against an excessive nose high attitude. Some airplanes will get off quickly only to settle back to the ground after climbing out of ground effect.
- Should you notice a vibration just before and immediately after take-off, apply brake pressure to stop the wheel rotation . . . your tires may be out of balance.
- Immediately feel out the controls . . . but gently. Do not overcontrol. Most homebuilts are quite sensitive to even small control inputs.
NOTE: If excessive pressure is required in any control, or if anything is amiss, abort the take-off immediately. However, if you must do so, don't chop the throttle suddenly. Retard it smoothly, otherwise you may encounter severe controllability problems. Land on the remaining runway, or straight ahead. This same rule applies to an engine failure immediately after take-off. Land straight ahead. Don't allow the airplane to stall. Maintain flying speed all the way down.
- A quick glance at the airspeed indicator at lift-off will provide you with the knowledge that the airspeed indicator is working, and this will, also, give you a rough idea of what your landing speed may be later. If you have a retractable gear, leave it down and locked for the first flight. A retracted gear would only add to your problems should an emergency develop.
- Climb out in a shallow climb angle at full throttle. If you used flaps for takeoff, you can milk them up now. Start a gentle turn after passing through 500 feet AGL so you won't get too far from the airport. Continue climbing as you turn downwind.
- Do not even think of retarding the throttle or changing any engine control settings unless the engine redline rpm is being exceeded. Many engine related take-off failures seem to coincide with the initial power reduction.
- If you used a fuel booster pump for take-off, you can turn it off now.
- Glance at the oil pressure, oil temperature and cylinder head temperature gage (if installed). If any indications are excessive, discontinue your climb and expedite a landing. Otherwise, continue to 3,000 feet and level off. Continue making gentle turns to stay over the airport.
- Adjust engine power and trim to cruise flight. Be on the alert for any unusual vibrations, strange noises or binding in any of the controls. Keep monitoring the engine gages. All O. K.? If not, immediately return and land.
- If everything is O. K., look around and relax . . . great, isn't it? If you have a chase plane, allow the pilot to pull up and look you over. You could also use the opportunity to compare indicated airspeeds.
If everything is quite manageable, clear your area and make a few power-on and power-off approaches to stalls. Complete (deep) stalls are not necessary. Merely slow the airplane to the point where the controls get mushy and a slight tail buffet becomes apparent. Careful. Some airplanes can stall/spin without much warning. Note your approach-to-stall airspeed indications and make a mental comparison of these with your take-off speed . . . assuming you remembered to look at it.
Everything may be going so good that you are tempted to try something else. DON'T! You'll have plenty of time for all that in follow-on flights. Stick to your original flight test plan.
Keep your flight short . . . say, 30 to 45 minutes.
- Run through your Pre-Landing Checklist, or at the very least go through that ol’ reliable GUMP check:
G = Gas
U = Undercarriage
M = Mixture
P = Prop
- Announce your intentions to land, and enter traffic. You may want to make a practice approach to landing. If so, use a power approach and don't get too low and too slow.
- If you have flaps, use them but watch that airspeed. Make your final approach at a speed at least 1.5 times higher than your earlier noted approach to stall speed. This is probably a bit high and may cause the airplane to float a bit, but you can, later, as you become more proficient in the airplane, reduce your approach speeds to suit.
- Be prepared to make a go-around if you are not satisfied with the approach, or are too "hot", and find you are overcontrolling and leveling off too high.
- Homebuilts with their smaller wing areas characteristically have steeper descent angles than do commercially produced aircraft. It is, therefore, wise to use some power all the way to touch down.
- On touch down, concentrate on keeping the airplane straight and let it roll out. Stay off the brakes if you can. Be gentle with them if you do have to use them.
- Clear the runway and taxi back to the flight line and to the congratulations that you have earned and deserve. It's 0. K. to grin and wave at your friends now.