AS 311 - Exam 1 Math Prep

8 flashcards · Other · by Nicholas Enoul

  1. **Round all answers to the nearest 1/10** How much work (W) is required to lift a Cessna 172 onto a maintenance stand given the following conditions: Aircraft weight: 2,058 lbs. Maintenance stand height: 5.3 ft. Formula to use: Work=Force∗DistanceWork = Force*DistanceWork=Force∗Distance Unit we want: foot pounds

    Answer: 10,907.4 Foot Ibs

  2. **Round all answers to the nearest 1/10** How much power (P) is required to lift a Cessna 172 onto a maintenance stand given the following conditions: Aircraft weight: 2,058 lbs. Maintenance stand height: 5.3 ft. Time: 3 minutes Formula to use: Power=Work/TimePower = Work/TimePower=Work/Time or Power = (force x distance) ÷ time Unit we want: Foot-pounds per minute

    Answer: 3,635.8 ft-lbs/min

  3. **Round all answers to the nearest 1/10** How much horsepower (Hp) is required to lift a Cessna 172 onto a maintenance stand given the following conditions: Aircraft weight: 2,058 lbs. Maintenance stand height: 5.3 ft. Time: 3 minutes Formula to use: Hrspower = Power (in ft-pounds/min) ÷ 33,000 Power = work ÷ time Work = force * distance Units we want: Ft-pounds/min

    Answer: 0.1

  4. **Round all answers to the nearest 1/10** What is the acceleration (A) of air (feet/sec2) that passes through a turbine engine during a static engine test given the following conditions: Airflow velocity at exhaust nozzle: 375 mph Time for air to pass through engine from inlet to exhaust nozzle: 1 sec. Formula to use: (final position - initial position) ÷ time Units we want: FPS

    Answer: 550 Explanation/Walkthrough: This question is basically just unit conversion. Since this is a static engine test, we can assume that the initial velocity/position is 0. Thusly, we only have the final velocity/position and 1 second. We need to change the 375 mph to feet per second. Convert this, and you will get 550 feet per second

  5. **Round all answers to the nearest whole number* What is the mass airflow (Ms) (lbs/sec) of a turboprop engine with the following criteria: Propeller diameter: 106 inches Airplane velocity: 218 mph Formula to use: MS = Pi (radius^2) (0.07647) (speed or H) Units we want: FPS

    Answer: 1,488 fps with a margin of 50.0 Explanation: this is another question that's almost exclusively unit conversion. For prop diameter, we need to divide it into two to get its radius (which is 53), then convert it into feet (which is roughly 4.42). For the velocity, we need to get it from mph to fps. Once converted, it should roughly be 319.73. Once we get all of that, we plug it into the formula and get the final answer from there.

  6. **Round all answers to the nearest whole number* How much net thrust (Fn) (pounds) is produced given the following conditions: Propeller diameter: 106 inches Airplane velocity: 218 mph <---- this is our V1 Prop wash velocity: 558 ft/s (fps) Time: 1 sec. Formula to use: Fn = [MS (V2 - V1)] ÷ Gravity MS = Pi (radius^2) (0.07647) (speed or H) Units we want: FPS Constants: Gravity = 32.2 fps Amospheric Pressure fr MS calc = 0.07647

    Answer: 11,087 with a margin of 200.0 Explanation: Once you calculate MS, this is even more unit conversion. You'll need to convert airplane velocity into FPS (which should be 319.73). Once you get MS and V1 corrected, input it in and you should get the answer! :D

  7. **Round all answers to the nearest 1/10** Calculate force (F) at the exhaust exit on a PT-6 turboprop engine given the following conditions: Area of tailpipe exit: 18.8 in2 Exhaust gas pressure: 28 psi Atmospheric pressure: 12.2 psi Formula to use: Force=Pressure∗AreaForce = Pressure * AreaForce=Pressure∗Area

    Answer: 297 (an attempt @ an) Explanation: We know the area, so we plug that in. F=P*18.8 in2 Now for the hard part. The reason why they gave us atmospheric pressure is so that we can calculate the total pressure. 28 psi - 12.2 psi = 15.8 (our total pressure) Then we plug it all in F = 15.8*18.8in2 F = 297.04

  8. The Rolls Royce Trent XWB engine flow rate is approx. 354 ft/s, the engine diameter is 118 inches, and the exhaust gas velocity is 312. Calculate gross thrust. Formulas to use: MS = pi * R2 * h * .07647 lbs3 MS(V2-V1) / 32.2 fps Units we want: Pounds/Second

    Answer: 2055.8 lbs/sec An attempt at an explanation: First, you need to calculate mass airflow After that, it's pretty simple, you just have to plug in the numbers. You multiply the difference of aircraft speed and exhaust velocity by airflow, then divide that by gravitational acceleration to get the gross thrust. 2055.8