Questions tagged [performance-calculation]

Questions about calculating the various measures of performance of an aircraft.

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7
votes
2answers
4k views

How does blade solidity ratio relate to thrust/power/torque of a propeller?

for quite some time I was using ABBOTT formula for static thrust estimation on a two-bladed propellers: $$ T=6.8\times10^{-5}\times D^{3}\times p\times RPM^{2} $$ $T$ is Static Thrust (N); $D$ is ...
5
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1answer
7k views

Is there a specific formula or way to calculate flex temperature for an Airbus A320?

I have hear of RTOW charts but I haven't seen any calculations with the runway length or slope. What is the formula or equation to finding flex temperature and V-Speeds?
6
votes
1answer
522 views

Is there an equation which allow us to perfectly match a helix propeller and an engine?

Is there an equation which allow us to perfectly match a helix propeller and an engine? I'm looking for an equation that allow me to correctly dimension an helix propeller for my engine. I mean that ...
1
vote
1answer
7k views

How to calculate the thrust of a piston or turboprop engine? [duplicate]

This spawns from a related question. Propeller-drive engines (piston/turboprops) seem to always list their output in horsepower or kilowatts, which are units of power. I want to know the engine's ...
5
votes
5answers
17k views

How do you convert true airspeed to indicated airspeed?

Is this something found in the POH? I know there is a IAS and CAS chart.
11
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1answer
17k views

How to calculate the Lift Coefficient for the A320?

I'm trying to figure out the lift coefficient of an A320. What I'm doing is the following: during cruise, the lift is equal to the weight of the aircraft ($mg$) so that I used the cruise table taken ...
8
votes
1answer
32k views

What would be the ground roll and total distance to clear a 50ft obstacle given these conditions?

I'm a student pilot, the question I am trying to answer is What would be the ground roll and total distance to clear a 50ft obstacle given an elevation of 5,000ft, altimeter 29.52, and a ...
8
votes
1answer
4k views

Why is Cessna 172 POH performance chart based on Pressure Altitude and Temperature instead of Density Altitude?

While calculating takeoff distance for Cessna 172, POH need to be used. POH charts has pressure altitude and temperature and then distance for those two known parameters. Does this mean if we have ...
5
votes
1answer
6k views

How to calculate required thrust for take-off knowing gross weight and L/D?

I know that many variables play into the required thrust for a take-off and for climb. Most of those specs boil down to a targeted gross weight, wing loading and L/D ratio. Intended flying speed range ...
3
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7answers
4k views

How does maximum speed vary with altitude?

Question: How does a commercial jetliner's highest possible groundspeed vary with altitude (assuming wind=0) ? My understanding is that drag decreases with altitude, therefore maxspeed increases with ...
1
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3answers
9k views

Is there a formula to calculate ground distance traveled given rate of climb and true airspeed?

I'm looking for a formula to calculate the horizontal distance (guess it is the Ground Distance) passed during the phase of ascent (or descent), having the rate of climb in ft/min and the TAS in knots....
8
votes
1answer
3k views

What are the meanings of various reference lines and sections in a take-off distance graph?

I am trying to solve a numerical problem related to determining take-off roll using a take-off distance graph. The parameters are Temp: 90F, Press. alt: 2000ft, wt: 2500lbs, headwind: 20 Knots. I got ...
7
votes
2answers
1k views

How is hypothetical max altitude of a helicopter calculated?

How do engineers calculate the hypothetical max altitude of a helicopter if the mass, altitude and length/curvature of blades are known?
7
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2answers
1k views

How does the FOVE system work with the Airbus FMS?

The Flight Operations Versatile Environment (FOVE) is a separate software system used with Airbus aircraft by dispatchers to determine performance data to enter into the FMS. There seems to be little ...
1
vote
2answers
5k views

How do runway declared distances affect my takeoff distance?

See these questions. What is balanced field length? What are runway declared distances? My multi-engine jet airplane uses a balanced field length concept. Most airports served by airliners have ...
10
votes
1answer
9k views

Why is “clearway minus stopway” used in V1 adjustments?

Illustrations and/or satellite imagery to explain the difference between clearway and stopway and explaining how they are used by turbine aircraft would be great. From B787 FCOM.
4
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2answers
3k views

How to calculate the Glide Ratio from Drag & Lift?

I know that $c_{d}=0.03 + 0.095c_{l}^2$. What is the glide ratio?
4
votes
1answer
6k views

How is the zero-lift drag coefficient calculated?

The drag coefficient is usually given as a funtion of the lift coefficient and the zero-lift drag coefficient ($c_{D0}$): $c_D=c_{D0}+k\cdot c_L^2$ How can I calculate/estimate $c_{D0}$?
3
votes
4answers
308 views

Can longer paths consume less fuel than the (shorter) great circle path?

Is the most fuel-efficient route between points A and B always along a great circle ? Although somewhat counter-intuitive, this comment on an aviation blog seems to suggest that longer paths (in ...
2
votes
2answers
2k views

What is the formula for estimating the maximum stationary thrust of a rotor as function of its diameter?

I am new! New to this forum and new to aviation (i normally deal with statics) so thanks in advance for beeing patient with me. Recently i was trying to figure out how much weight a rotor can lift as ...
6
votes
1answer
315 views

Does one-engine cruise consume less fuel than two-engine cruise?

Scenario 1. A two-engine airliner experiences rapid depressurization and makes an emergency descent to 10,000 ft, and diverts to the nearest airport. Scenario 2. The same two-engine airliner ...
6
votes
1answer
846 views

How to calculate the DC-4 landing distance with this graph?

Can someone give me a clear explanation on how to calculate the landing distance of the Douglas DC-4 with the following graph? And why is the Temperature variable not in the graph, because temperature ...
4
votes
4answers
2k views

How do you calculate trip fuel based on hourly fuel burn rates?

I am working on a small personal project that uses fuel burn data about specific aircraft to calculate the total fuel required for a trip. The data looks like this: ...
4
votes
1answer
1k views

Why does lower atmospheric pressure produce higher EPR (thrust)?

Recently, I read manual about engine, PW JT8D-217A/C, and there is a chart making me so confused. Manual show the reference table tells you what number, EPR, is normal in specific temperature and ...
4
votes
1answer
4k views

What are fuel biases?

Does anyone have an idea of what is it? From what I gathered from the web, it seems that this is the margin of error between the actual, real fuel consumption of the aircraft and the fuel consumption ...
4
votes
3answers
13k views

What is the maths behind the descent rate calculation?

The descent rate calculation states that descent rate is calculated by 'groundspeed / 2 * 10'. Another document stated that the ground speed should be multiplied by 5 (or more accurately 5.2) to ...
3
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2answers
2k views

What makes V1 one or two knots less than Vr on this performance table?

(B738 AFM, 0-2000 feet elevation, up to 27°C) Example of V1 and Vr differences. The table shows that the V1 speeds are invariably one or two knots lower than their matching Vr speeds. Given that V1 ...
2
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1answer
4k views

How does the FAA compute the values in TPP's Climb/Descent Table?

The inside back cover of the FAA Terminal Procedures Publication contains a table headed “CLIMB/DESCENT TABLE,” excerpted below. Source: FAA, p. 19 How do required ascent or descent ...
1
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1answer
6k views

How do you calculate indicated airspeed on a flight plan?

I'm planning my cross country journey for my flight test and it seems I forgot how to calculate my indicated airspeed. The indicated airspeed must be from the POH, right? The the true airspeed is ...