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Flight model testing procedures (read before posting)


When reporting issues with a particular aircraft's FM (speed, climb, etc). Please use the following testing methods for reporting a bug or error. No reports should be submitted based upon stat card information, or module information. They must be tested on the actual plane under "Testing Conditions"

*All Test should be performed with the reference model (select this for your test flight) on Full Aerodynamic control under either RB or SB settings. Preferably with a joystick.
 

1. Ground tests

 

In a test flight as you appear on the airfield first of all you must check plane controls. Their movement must map the stick manipulation and it should be smooth, therefore it is better to test planes with you Axis nonlinearity setting equal to 1. Then we test trim controls - its availability must be same as in the period documentation.

 

Next you start the engine. As you've started the engine rpm must be equal to figures stated in the period documentation. Then we switch to manual engine controls, set the airscrew pitch to 100% and go down on the brakes, smoothly adding power till we can no longer hold the plane stationary with the use of breaks. Here we note down rpm settings and comparing them to period documentation as well. After that you investigate usage of mixture control, airscrew pitch, supercharger, radiator grills. All of it must comply with period documentation.

After you are done with all of the above, you can test plane's taxiing. You begin moving at ~20 km\m in S-turns applying left and right brake pedals (if your plane model had separate breaks). 

 

Next thing to do is to stop the aircraft, add the power up to 20-30% and then you push rudder in differnt directions. If your plane has a tailskip, then the plane shouldn't move, otherwise it should begin moving.

Then you can perform following test - you speed up to 40-50 km\h, idle the engine and wait till plane slows down to 20-30 km\h and start operating rudder without applying breaks. The plane should make turns only if it have steerable tailwheel

 

After that we will check air-flowing the elevator. We push the breaks and gradually increasing THR to 40-45-50-55+ and smoothly push the stick full forward so that we will find rpm when the plane raise its tail. We should also try to balance plane via rpm and elevator position. Thus we will also will check if the center of gravity and the anti-nose-over angle of chassis are set up right

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2. First test flight and landing

 

As your plane is on the ground, first of all try your best to remember hood position on the horizon. You will need that 'picture' later to make a perfect landing. Classical landing of an aircraft with a tailwheel is a 3-point landing, so you will need that skill to estimate landing speed correctly. Landing speed is a speed at which you aircraft will make 3-point landing with flaps and gear extended

 

You start off with short speedy runs on a runway. At this stage you need to check how plane reacts to the throttle increase, depending on how hard you operate it. You will also test if the airscrew torque effect is tuned up correctly - if it rotates clockwise you will need to push rudder left in order to compensate yaw effect. And if it rotates anti-clockwise you will push the right rudder pedal . Yaw effect may vary greatly on different aircrafts, to find out how significant it was, you will need to study pilots handbook. But the overall tendency is the more smoothly you add throttle the easier yaw effect should be.

 

In most cases take-off should be performed without extending flaps (unless period docs state the other). You accelerate smoothly to take-off power settings, constantly compensating yaw effect, at 50-60 km/h you push the stick ~1/3 beyond neutral and we expect the plane to lift it's tail. As this happens, we slightly pull the stick back to fix the take-off position of the plane and we proceed the run and note down the speed at which plane will take off to compare it later with your documentation.

 

 

Some airplanes had an insufficient aileron effectiveness at low speeds, so take-off and landings were performed on higher speeds and landing could be performed on two wheels

 

After you are airborne, you must gain more speed. Some planes have low thrust-to-power ratio so they must fly strictly horizontal to get enough speed to start climbing. Raise gear and after you've reached recommended speed, trim out aircraft and start climbing. As you'll reach 150-200 above the airfield meters make a first turn and at 300-400 meters stop climbing, set cruising speed and trim out again. For the most aircrafts you can find cruising speed and appropriate engine mode in pilot's handbook. If the aircraft is tuned well these values must match.

 

After these checks you can make a second turn and on the way to third one you check the general control/stability check. Aircraft must react properly on quick, short stick manipulations. If you cut the throttle you should feel that you'll have to operate stick less shortly to make the plane perform the same way. If the speed is close to stalling, you will have to make full use of your stick 

 

As we closing in to the 4th turn we reduce the throttle and reduce the speed to extend gear safely (check your documentation for those values) and trimm out the plane. Extend the gear, at that very moment on a trimmed out plane you should feel that nose goes slightly down. After 4th turn you set airscrew pitch to 100% and head the plane on the approach trajectory, extend landing flaps. As you you've extended them, you should feel that nose goes up or down (depending on the aircraft) and plane should start to loose speed rapidly, so that you will have to add throttle to maintain approach speed

 

As you reach the runway, you reduce the throttle and start leveling up. Final leveling up should be performed at 0.5-1 meter above the runway. At that stage you try to level that plane the very same way you remember it standing on the airfield and you wait till it touches the ground. At that very moment you will find your landing speed. To define it correctly, you must perform a 3-point landing with no jumping off

 

After you've landed safely pull the stick fully back and pay attention to plane's behavior on the run. Plane should react on elevators down till 30-50 km/h speed

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3. Stall speed

 

During this stage you will check engine settings. As you appear on the airfield set radiator and mixture to 100%. Proceed to take-off on WEP and ease down to take-off mode as you reach time limit of WEP, proceed climbing. When it's time limit is also reached, use nominal mode (mode which is meant for continuous use)

 

Then you should define stalling speeds (with flaps in combat, take-off and landing settings plus with no flaps). It is recommended to perform that at the same altitude of 500-1000 meters

 

To check stalling speed do as follows:

1) Set the THR to 0%

2) Reduce speed and maintain altitude (+- 5 meters), with no rolling, banking, or sideslip (use controls in the cabin or virtual cockpit)

3) Note down IAS at which plane will stall

4) Push stick forward to prevent spin

 

Repeat measurements at least three time to exclude chance of an error. Experiment with the different flaps settings, note down results and compare them with your documentation.

 

After you've defined stall speed in horizontal flight you do the same for gliding at vertical speed of ~5-8 m/sec. To check that you reduce IAS to +20-30 km/h above speed of stall and set the plane gliding, reducing speed further, while maintaining constant rate of decent (for example 7 m/sec for all the measurements). Received values must not differ with stall speed in horizontal flight.

 

Next thing to do is check stall speeds in take-off mode. It's quite convenient to alter checks in gliding mode with take-off mode.

At altitude of 500 meters we reduce the speed to 30+50 km/h above stall speed, then:

1) Add throttle to take-off mode and start climbing maintaining that speed

2) As we find proper angle for that we begin to increase tang angle so that planes starts to loose speed smoothly

3) We define stall speed in a climb on take-off mode

 

This values should be slightly lower than the previous ones as you experience extra airflow around the airfoil

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4. Testing climb rate

 

To make in-depth test of climbing performance, you have to build polar of climb rates. It's easy to make, but quite time consuming (up to 1 hour per aircraft). Start a test flight on fully fueled reference modification of the plane (it makes sense to enable 'unlimited fuel' option). Take-off, set pitch and THR to 100%. Get the plane to optimal climb speed (check your documentation) and set climbing angle so that IAS maintained within 2 km/h range, don't let sideslides. At ALT of 300-400 start stopwatch and measure time to get 500 meters of altitude. Repeat measurement 2-3 times to receive correct data

 

Next step is to repeat tests, increasing climb speed in 20 km/h steps. Do so until climb rate falls bellow 5 m/sec mark. After that make tests at speeds bellow optimal in 10 km/h steps, till the plane won't be able to steady climb at all. This limit should be around stall speed or slightly less

Test with differing flap positions and with gear up/down. Do this 4-5 times so a complete picture of FM behavior can be established.

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5. Testing of maximum speed in level flight.
a) Testing is performed strictly according to the conditions given in the period documentation for the aircraft. ( Example: radiator shutters open by 20%, 100% of the screw pitch, thrust the WEP )
b ) If these parameters test conditions are not present, you should use the standard test conditions, namely:

  1. Manual engine control
  2. The radiator should be fully closed (0%)
  3. 100% pitch on the Prop (max facilitated)
  4. Maximum Thrust ( WEP)
  5. Fuel load set to 100%

c) Methods for measuring the maximum speed

  1. Using a shallow dive to accelerate into a height: Firstly you need to collect a greater height than the one on which you want to make a measurement of the maximum speed. And then dive into the appropriate height (based upon period docs) and hold the aircraft in a level horizontal flight. Secondly as soon as the acceleration drops off and your speed is a constant value (during at least 20 seconds , the height may not be changed), note the maximum speed. This method allows you to measure the maximum speed of the aircraft with or without WEP and with best aerodynamic settings possible. This method works best for aircraft that run under hotter engine conditions.
  2. Acceleration in level flight: For this one must first reach the desired height for obtaining a speed measurement based upon the period documentation ( Note: Perform the test with rated engine settings for that plane, in order to avoid overheating of the engine ). Keep the aircraft in level flight while you wait for the moment when the speed stops growing ( at least 20 seconds at constant speed reading ). Then note the values obtained. (This method is not suitable for aircraft operating at higher engine heat capacity)
  3. Perform at least three measurements of the maximum speed at all heights shown in the documentation, and note the average value in each set of three measurements.

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