Questions tagged [performance-calculation]
Questions about calculating the various measures of performance of an aircraft.
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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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1answer
59 views
How do you calculate Profile Drag?
second year aeronautical engineering student here. I'm doing some aerodynamics coursework but have run into a problem.
I've read through the answers to the question "what is profile drag?" but ...
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0answers
88 views
For Airbus pilots, what is your TOD calculation methodology?
During A330 training, various instructors will have many different types of equations and gateways used to confirm the descent profile and whether or not they are above or below glidepath.
The ...
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2answers
2k views
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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1answer
1k views
What fomula 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 ...
4
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2answers
356 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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0answers
57 views
What is a good and simple software for calculating propeller thrust and required power?
My main requirements:
Calculate propeller thrust with big range of the altitudes (0 - 200 km) or to have air pressure input parameter, which I can type. For example pressure for 152 km is $4.98\...
3
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1answer
107 views
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 ...
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1answer
274 views
What is the average climb gradient of an aircraft during the takeoff and early phase of a departure procedure?
On chart plates it is written the minimum climb gradient with which an aircraft should climb for obstacle clearance or after ATC request (for traffic flow management etc.).
However, since this is the ...
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2answers
117 views
Are compressor maps for multistage compressors drawn for one blade row or the whole compressor?
Apologies if this is a stupid question.
I am a little confused about compressor maps.
Are compressor maps such as this one, drawn for one blade row only or the whole compressor?
(source: Wikimedia)
...
6
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1answer
303 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 ...
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1answer
160 views
Do takeoff (or other) performance calculations for jet aircraft take into account the type of fuel being used?
Jet aircraft can use any of a number of different fuels:1
Jet A-1 is a straight kerosene, not that much different from what you used to buy for committing arson fuelling portable space heaters.
JP-8 ...
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2answers
354 views
How do I estimate piston aircraft fuel efficiency?
Is there any way to figure out or calculate fuel consumption of piston engines for aircraft? I'm looking at different engines in a book, and while jet engines have useful values like thrust, bypass ...
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1answer
73 views
Do aircraft performance figures include corrections for areas with especially strong or weak gravity?
The strength of gravity at the Earth's surface is not constant, but varies from place to place by as much as a few percent:
(Image by NASA.)
As a result, an identically-loaded aircraft weighs less ...
2
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1answer
366 views
How would you use the mental clock code to solve this dead reckoning problem?
Can someone explain the question below in details?
You plan to fly a cross country flight at 2 000 feet at a true airspeed of 120 knots. Your track is 270° (True) and the wind is from 225° (True) at ...
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1answer
267 views
How would I calculate CG in this practice problem?
As I'm studying PPL theories, I've encountered with this kind of a question below and it would be great to understand the principle behind the calculation of the 'CG'
Calculated take-off mass = 2300 ...
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1answer
261 views
How is altitude correlated with true airspeed?
I am trying to understand the BADA 3.0 dataset (specifically I am looking at Performance Summary Tables):
E.g.
What is not obvious to me is why those tables mention only single TAS for specific FL.
...
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3answers
4k views
How to calculate service ceiling and absolute ceiling in PA-44 Seminole?
I am hard to understand to calculate service ceiling and absolute ceiling in PA-44 Seminole. Is there anyone know how to calculate it in the condition(T/O weight: 3599.24 L/D weight: 3354.44 PA:2329 ...
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2answers
322 views
What margin of error should one reasonably allow regarding aircraft performance?
This question generated a lot of discussion around amateur pilots often making the mistake of calculating aircraft performance based on perfect conditions and not allowing for a 'safety factor' (i.e. ...
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2answers
300 views
How can I correct an expected climb rate for density altitude?
If a flight manual (for a naturally aspirated piston engine plane) gives a figure for a best climb rate at standard temperature and pressure, is there a way to adjust that figure for a different ...
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2answers
80 views
Is the route which takes the least time always the one with least fuel-burn?
Geographically longer paths may require less fuel than the shortest (great circle) path. But what about time ?
Is the most fuel efficient route always the one that has the aircraft in the air for ...
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4answers
301 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 ...
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0answers
161 views
How are the takeoff V speeds calculated? [duplicate]
What is the actual formula for calculating the takeoff V speeds of an aircraft with any configuration? Specifically, I mean V1, Vr and V2
I know there are many factors, but what are they specifically ...
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1answer
344 views
What are the takeoff and landing distances of motor gliders?
I'm doing some estimations of weight and thrust loading for a college project, and in the formula below the landing distance is not a variable, but should be estimated using similar aircraft and usual ...
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7answers
3k 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 ...
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2answers
3k 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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2answers
410 views
How can I calculate a pitch/power table?
I want to make a pitch and power table for C172s based on calculation, just like I attached above.
I picked up this table on internet, but I'm not sure where it comes from.
Do you have any ideas how ...
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1answer
516 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 ...
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1answer
234 views
Where can I find climb and cruise performance charts for a specific aircraft?
I'm looking for climb and cruise charts for a cirrus sr20 G3, but I can't find them in the POH? where are these charts typically located?
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1answer
389 views
How to compare turboprop engines and with which values?
I have found this website that lists a lot of turboprop engines. I would like to compare them with as few values as possible. As an example, there are tons of different values that describe a jet ...
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2answers
2k views
How do I calculate FPNM for standard take-off minimums?
I have trouble understanding and calculating FPNM for standard take-off minimums.
As I understand, the formula is: (Ground speed)/60 * FPNM = FPM
Let's say the ODP says:
565' per NM to 2800, or ...
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1answer
933 views
How do I determine the engine thrust required to give a specific climb rate?
New pilot here and I am playing around with a flight simulator game for the B737-800. I need some help understanding where/how one can find out if one has enough engine thrust (%N1) to meet a required ...
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2answers
738 views
Propeller Characteristics at Different Altitudes
Assuming I have a propeller with a given diameter (D), pitch, blade twist, and number of blades, I can theoretically analyze discrete airfoil sections in XFOIL and come up with lift and drag polars ...
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1answer
735 views
What are the Boeing 777 thrust calculations? [closed]
Can someone show typical calculations for a Boeing 777 jet engine for the following criteria:
Take off thrust of the engine at 170 mph take off speed and 45 degrees F
Cruising thrust required at 500 ...
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2answers
293 views
How can I determine specific heats of gases for turbojet engine calculations?
I'm in a combustion lab and we are performing experiments on a turbojet engine. However, I am having some trouble calculating the exit velocity and compressor/turbine powers of the engine.
Consider ...
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1answer
476 views
Why are the positive points in a V-n diagram associated with pitch maneuvers?
For an aircraft with such flight envelope, the flight conditions in point A, C and D are ...
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1answer
2k 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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2answers
510 views
Why do some multi-engine aircraft have accelerate-go distance in their performance charts and some don’t?
I'm curious about why some airplanes have accelerate-stop distance (ASD) and accelerate-go distance (AGD) in their performance charts and some don’t include that. Does anyone know why?
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1answer
2k views
Calculating Ground Speed - E6B vs Pythagorean Theorem
I have been trying to create an excel formula for calculating the ground speed of an airplane using the TAS, Course, Wind Dir, and Wind Velocity.
The issue that I am finding is that I can't properly ...
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185 views
How can I calculate different airspeeds given atmospheric data?
I want to calculate various airspeeds (TAS,CAS,IAS,..) given a certain altitude. With the given altitude I can figure out the pressure, density, speed of sound, temperature, and viscosity. However, I'...
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2answers
2k views
How to realistically model propeller static thrust?
I am graphing static thrust vs prop diameter for a 600 kW motor and a prop diameter up to 5 m. I have seen the post 'What is the equation for calculating static thrust?' and using its formula and ...
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0answers
114 views
How are the landing, takeoff, and cruise speeds calculated for my homebuilt ultralight?
How can I calculate the takeoff, landing, and cruise speeds of my ultralight with a total weight (with load) of 120 kg, average air density of 1.23 kg/m3, wing area of 13.18 m2, and a coefficient of ...
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1answer
5k 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 ...
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2answers
8k views
How do we calculate top of descent (TOD) in flight? [duplicate]
What is the in-flight trick?
I know how to calculate it in theory, but how can I calculate it fast? For example, I know I can use this formula for calculating the rate of descent:
[ground speed + ...
6
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4answers
236 views
What experimental techniques should one employ during cruise flight to determine correct airspeed to fly for max range in a headwind or tailwind?
Theory demonstrates that one ought to increase speed in an headwind, and decrease speed in a tailwind to achieve maximum range. A lengthy discussion on the theoretical solution was answered, though ...
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3answers
886 views
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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2answers
10k views
How to ballpark IAS vs TAS?
Is there some reasonably accurate ballparking formula to allow for quick conversions between IAS and TAS as a function of pressure altitude and difference of ground temperature relative to standard ...
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1answer
152 views
How should I interpret the Douglas DC-4 approach climb performance chart?
Can someone explain what "C = .04 Vso2" means as the "denotes required rate of climb?". I assumed the point at 6500 ft altitude and 60,000lbs landing weight will mean that the required rate of climb ...
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3answers
2k views
Does the dew point affect density altitude?
I am looking for the most accurate formula to calculate the Density Altitude (DA) to use it for calculating aircraft performances during landing.
Now I found the following formula:
DA = PA + [120*(...
3
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1answer
299 views
Why do DC-4 landing performance charts have different values for the intended and alternate destinations?
I am studying the landing performances of the old Douglas DC-4 and there are a lot of different landing performance charts available. The pilots can use different flap settings during landing like 45, ...
