# Questions tagged [performance-calculation]

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

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### 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?
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### 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 ...
9k views

### How can the wind speed and direction be calculated from on-board measurements?

I am currently learning C++ on my own in my spare time. I am writing a little application that will help me while at work. I have come across a situation where I have some given values, but im not ...
30k 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.
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### How can true altitude be calculated from pressure altitude, temperature and altimeter setting?

The manual that came with my Jeppensen E6B has the following sample... If an aircraft is flying at 12,500 feet with an outside air temperature of -20C and the altimeter is set on 30.42 inches of ...
5k 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?
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### 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 ...
• 151
11k 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 ...
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### 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 ...
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### 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 ...
• 737
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### What is a Second Segment Weight Limit?

I am very interested in the principles of take-off performance optimization. During my research I found an interesting picture, showing the software used by a European carrier. However, the output ...
1 vote
15k 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....
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### 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 ...
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### 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?
38k 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
• 263
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### 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 $c_{D0}$?
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### 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 ...
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### 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 ...
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1 vote
6k 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 ...
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### Why does the takeoff N1 limit start to decrease below 30°C OAT?

It's easy to understand why the takeoff N1 limit decreases with an increase in the OAT in the chart above; the engines get less dense air at higher temperatures, and less dense air means less engine ...
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### 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.
4k views

### Why aren't large, low-speed propellers widely used?

I am trying to calculate different propellers for the simple case like helicopter moving slow up like 1 m/s or staying/hanging in one place. From generic physics point of view it is more efficient to ...
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### 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 ...
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### Why is my calculated seat-miles per gallon of small aircraft higher than of big aircraft?

I've calculated the seat-miles per gallon for three planes. This factors in the speed; it basically means how much does it cost to transport 1 person 1 mile. Plane Seats Cruise (MPH) gph seat-mpg ...
29k views

### What formula to use for calculating pressure altitude?

I'm having some trouble making my calculations of pressure altitude match those in apps and text books. I'm using the formula from Wikipedia: (29.92 - altimeter setting) * 1000 + airport elevation ...
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### 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 ...
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### How to perform a "first principle" performance calculation?

I am a PhD student on flight dynamics and control. This week I was given an assignment to do some research on methods of aircraft performance calculation. After some search on the Internet, I found ...
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### 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: ...
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### What are the equations to compute takeoff and landing distance?

I am flying a Piper 28-336 Dakota. Based on this paper I was able to reproduce the take-off distances from the POH and incorporate the calculations directly in Excel. It can be seen that the effects ...
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### 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 ...
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### 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 ...
6k views

### How to calculate the Gust Envelope?

I am trying to draw the V-n Diagram for a small aircraft I built, but I am stuck in the gust envelope part. I know how it is supposed to look. However, I am having a hard time calculating it. I would ...
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### 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 ...
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### How do I use the takeoff and landing distance charts in the C172 POH?

Can anyone explain how to calculate takeoff and landing distances using the chart for C172s, and please give me an example?
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### What is the correct term for the type of performance chart where curved lines are followed?

What is the correct term for the type of performance chart where, from a starting location, curved lines are followed to various reference points to eventually find a solution? For a specific example, ...
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### 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 ...
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### Is reducing V1 a viable option for pilots when the ASDA is shorter than the ASDR?

Let's say you were planning to ferry some passengers and cargo in a jet but after some calculations found out the ASDR (Accelerate-Stop Distance Required) was greater than ASDA (Accelerate-Stop ...
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### 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 ...
1 vote
2k views

### How to calculate the induced drag coefficient?

In an exercice of Flight mechanic, I have to compute the drag coefficient at zero lift: $C_{D0}$.We saw in class two ways to find it : $$C_{D0} = \frac{\pi AR e}{4E_{max}^2}$$ With $AR$ the aspect ...
1 vote
5k views

### How can I calculate takeoff distance in a generic way?

I want to build a generic performance app. For many of the aircraft the only available method is using the takeoff charts manually (I'm not referring to the more simple-to-calc short field charts but ...
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1 vote
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### 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 ...
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