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Pilot`s Notes Airacobra Pilot`s Notes

Pilot`s flight operating instructions for ARMY MODEL P-39Q-1 AIRPLANE



a. BALANCE DIAGRAM AND CHART. - Pilot should make a thorough study of the balance diagram and chart in section III.

b. It is essential that the pilot DETERMINE THE GROSS WEIGHT by referring to the WEIGHT AND BALANCE CHART in section III. Check the listed basic and alternate tabulated itoms against those loaded in the airplane. If the airplane is loaded in accordance with the "Basic Load Items" whose weights are entered under two loading conditions in the "Alternate Loading (Pounds)" column, the gross weight will be found listed at the bottom of the chart. If any Items tabulated in the "Pounds" columns are omitted in the loading of. the airplane, deduct the weight of these missing items from the "Gross Weight" and the answer will be the correct gross weight as the airplane Is actually loaded.

c. FLIGHT OPERATION INSTRUCTION CHART in section III is provided for flight planning purposes. The following outline may be used as a guide to assist personnel in their use in FLIGHT PLANNING.


If the flight plan calls for a continuous flight where the desired cruising power and airspeed are reasonably constant after take-off and climb to 5000 feet, the FUEL REQUIRED and FLIGHT TIME may be computed as a "single section flight."

(1) Within the limits of the airplane, the fuel required and flying time for a given mission depend largely upon the speed desired. With all other factors remaining equal in an airplane, speed Is obtained at a sacrifice of range, and range is obtained at a sacrifice of speed. The speed is usually determined after considering the urgency of the flight plotted against the range required. The time of take-off is adjusted so as to have the flight arrive at its destination at the predetermined time.

(2) Select the FLIGHT OPERATION INSTRUCTION CHART for the model airplane and gross weight to be used at take-off. Locate the largest figure entered under "gph" (gallons per hour) in column I on the lower half of the chart. Multiply this figure by the number and/or fraction of hours desired for reserve fuel. Add the resulting figure to the number of gallons set forth in the chart footnote No. 2, and subtract the total from the amount of fuel in the airplane prior to starting of engine. The figure obtained as a result of this computation will represent the amount of gasoline available and applicable for flight planning purposes on the RANGE IN AIR MILES section of the FLIGHT OPERATION INSTRUCTION CHART.

(3) Select a figure in the fuel column equal to, or the next entry less than, the available amount of fuel in the airplane as determined in paragraph I.e. (2) preceding. Move horizontally to the right or left and select a figure equal to, or the next entry greater than, the air miles (with no wind) to be flown. Operating values contained in the column number in which this figure appears, represent the highest cruising speed possible at the range desired; however, the airplane may be operated in accordance with values contained under OPERATING DATA in any column of a higher number with the flight plan being completed at a sacrifice of speed but at an increase in fuel economy.

(4) Using the same column number selected by application of instructions contained in paragraph I.e.(3), determine the indicated air speed and gallons per hour listed at sea level in the lower section of the chart under the subtitle OPERATING DATA. Divide this "IAS" into the air miles to be flown and obtain the calculated flight duration in minutes, which can then be converted into hours and minutes and deducted from the desired arrival time at destination in order to obtain the take-off time (without consideration for wind). To allow for wind, use the above "IAS" as ground speed and calculate a new corrected ground speed with the aid of a flight calculator or by a navigator's triangle of velocities.

(5) The airplane and engine operating values listed below OPERATING DATA In any single numbered column are calculated to give constant miles per gallon at any altitude listed. Therefore, the airplane may be operated at any altitude and at the corresponding set of values given so long as they are in same column listing the range desired.

RANGES listed in column I under "Max Cont Power" are correct only at the altitude given in the chart footnote 1, and the engine and airplane operating data listed under OPERATING DATA will give constant miles per gallon if operation is consistent with values set opposite the listed altitudes.

(6) The flight plan may be readily changed at any time enroute, and the chart will show the balance of range at various cruising powers by following the "INSTRUCTIONS FOR USING CHART" printed on each chart.

d. If the original flight plan calls for a mission requiring changes in power, speed, gross load or external load, in accordance with "GR WT" or "EX-TERNAL ITEMS" increments shown in the series of "FLK3HTOPERATION INSTRUCTION CHARTS" provided, the total flight should be broken down into a series of individual short flights, each computed as outlined in paragraph I.e. in its entirety, and then added together to make up the total flight and its requirements.


(1) In the event of war operations, secure radio frequency assignment for the flight.

(2) If radio model SCR274-N is installed In the airplane, be sure correct transmitter Is installed and tuned for proper frequency.

(3) If radio model SCR522 is installed in the airplane, be sure correct crystals are installed for proper frequency.

(4) ENTRANCE TO THE COCKPIT is made through the right-hand door. The door is opened by pushing in the upper end of the flush handle causing it to hinge out, uponwhich it can be pulled upward, opening the door.


1. Special check for night flying.

(1) Turn battery switch (figure 5) "ON."

(2) Turn cockpit lights (figure 5) "ON." The three cockpit lights are all controlled by the one switch.

(3) Turn left fluorescent light (figure 5) "ON."

(4) Turn right fluorescent light (figure 5) "ON."

(5) Test-operate gun sight rheostat (figure 5).

(6) Test-operate the landing light by first operating landing light motor switch (figure 6). When light is extended turn on the light switch (figure 6) for not over 3 to 5 seconds. Test complete, operate motor switch retracting the light.

(7) SIGNAL LIGHT. - A removable signal light is located on the right-hand cabin door. The light is operated by a switch located on the light.

b. Check for all flights.

(1) Ignition switch (figure 5) "OFF."

(2) Fuselage guns switch (figure 5) "OFF."

(3) Wing gun switch (figure 5) "OFF."

(4) Cannon switch (figure 5) "OFF."

(5) Landing gear control switch (figure 5) "OFF.

(6) See that control of landing gear clutch handle (figure 9) is in position for electric operation of the landing gear.

(7) Flap control switch (figure 5) "OFF."

(8) Generator switch (figure 6) "ON."

(9) Parking brake "ON." To set parking brakes depress brake pedals (figure 5), and pull out on parking brake handle. (See figure 5.)

(10) Adjust rudder pedals for correct leg length by pushing outboard on the spring-loaded lever on the outer side of each rudder pedal, adjusting them to length and then release the lever, locking them in place. BE SURE BOTH PEDALS ARE ADJUSTED EQUALLY. Check for full right and left movements of the rudder.

(11) Check for free movement of control surfaces.

(12) Check oxygen control valve and supply.