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Questions tagged [performance-calculation]

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

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18 votes
4 answers
3k views

Why do we still interpolate in performance tables?

I'm getting my Private Pilot License. In the coursework, we learn about flight planning, which requires looking at performance charts for your particular aircraft. These charts in my case are tables ...
Baron Biscuit's user avatar
12 votes
4 answers
15k views

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 ...
dazedandconfused's user avatar
11 votes
4 answers
4k views

Why does V1 increase with headwind and decrease with tailwind?

Can someone explain why V1 increases with headwind and decreases with tailwind? I read such a phrase in my ATPL(A) performance textbook, but without further explanation.
Konrad's user avatar
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11 votes
2 answers
3k 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 ...
lemonincider's user avatar
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11 votes
2 answers
12k views

What are the takeoff and landing speeds of a Learjet 45?

I am a fairly new enthusiast to flight simulation. I would like to know what are the takeoff and landing speeds of a Learjet 45? If they are not fixed, what factors influence those speeds?
John Keenleyside's user avatar
11 votes
1 answer
23k 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 ...
Afe's user avatar
  • 1,501
10 votes
2 answers
7k views

Is the takeoff power always maximum?

I used to think that for commercial aircraft from Airbus, Boeing, Embraer, etc., the take off power was always maximum and selected by the TOGA selection on the thrust levers. But I have been told ...
Jean's user avatar
  • 304
10 votes
2 answers
11k 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.
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9 votes
1 answer
3k views

How does a fighter pilot calculate approach/landing speeds?

Let's say an F/A-18C returns to land after expending some payload. Fuel burned and weapons released made the plane lighter. I guess the aircraft computer can tell the pilot the actual weight of the ...
O'Terror's user avatar
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9 votes
2 answers
1k views

Why do helicopter performance charts for hover out of ground effect (HOGE) have a "knee"?

Have a look at the following performance charts from Section 5 of Robinson R-22 Pilots Operating Handbook for hover out of ground effect (HOGE). If the temperature and gross weight are known, the ...
Igor's user avatar
  • 107
9 votes
3 answers
2k views

Why do propellers have less theoretical range (i.e. range ignoring impatient passengers wanting to go fast) than jets, despite greater efficiency?

I was playing around with the breguet range equation recently, and came across a suprising result, that propellers have less range than jets, despite having greater efficiency. The range equation for ...
Anonymous Person's user avatar
9 votes
3 answers
6k 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 ...
FlegmatoidZoid's user avatar
9 votes
1 answer
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 ...
Justin Sellers's user avatar
9 votes
1 answer
7k 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 ...
pmoubed's user avatar
  • 2,035
9 votes
6 answers
5k views

Does an increase in air temperature actually improve aircraft performance?

Mainly because of what pilots learn about density altitude and aircraft performance, any idea that an increase in temperature could improve performance seems counterintuitive. And indeed it is. Here's ...
ryan1618's user avatar
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9 votes
2 answers
2k 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?
sexy_koala_juice's user avatar
8 votes
4 answers
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 ...
Zlelik's user avatar
  • 183
8 votes
1 answer
985 views

Why do we calculate 25% more of TODR?

In general aviation aircraft, we are being told to calculate TODR (takeoff distance required) using AFM and TODR x 1.25. Why do we need the value with 25% added?
Krishna Kanth's user avatar
8 votes
1 answer
620 views

Why does Vr increase with lower air density and decrease with higher air density?

Can someone explain why Vr increase with lower air density and decrease with higher air density? I read such a phrase in my ATPL(A) performance textbook, but without further explanation. As far as I ...
Konrad's user avatar
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8 votes
1 answer
6k 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 ...
yankeemike's user avatar
8 votes
1 answer
236 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 ...
JM93's user avatar
  • 263
7 votes
3 answers
842 views

Mathematical function in performance diagrams

I have taken upon myself to digitise some scanned old performance diagrams, e.g. roll distance as function of mass and OAT, TAS as function of power setting, etc. The obvious goal is to allow the ...
Niclas Börlin's user avatar
7 votes
1 answer
664 views

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 ...
Isaiah Taylor's user avatar
7 votes
1 answer
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 ...
OneChillDude's user avatar
  • 2,170
7 votes
2 answers
1k views

How can I calculate the C.G height for an Aircraft?

before I continue I would like to thank you guys beforehand for the help. I am new to this forum and in aviation in general. I am helping my professor to obtain the C.G coordinates in x, y , z for a ...
Kaelan's user avatar
  • 73
7 votes
1 answer
1k 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 ...
lemonincider's user avatar
  • 7,565
7 votes
2 answers
17k 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 ...
GJ.'s user avatar
  • 512
7 votes
2 answers
2k 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 ...
TomMcW's user avatar
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7 votes
1 answer
516 views

For jets, how can we show that 1/2*ρ*V^2 is equivalent to 1481.3*δ*M^2?

In Roskam's book, we find the following relationship given for climb performance in jet aircraft: Thrust requested = $D$ = $C_d \cdot (1/2 \cdot \rho \cdot V^2) \cdot S = C_d \cdot (1481.3 \cdot \...
d.pensopositivo's user avatar
6 votes
4 answers
19k 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 ...
user avatar
6 votes
1 answer
651 views

How is Fuel needed to be consumed calculated when MTOM and Actual Mass is known

I'm practicing for my EASA PPL(A) exams and one of the questions I came across looks like this: How much taxi fuel must be consumed before take-off to reduce the aircraft mass to the maximum take-off ...
Tudor Ravoiu's user avatar
6 votes
1 answer
1k 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 ...
JM93's user avatar
  • 263
6 votes
2 answers
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?
Liam Baron's user avatar
6 votes
2 answers
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 ...
MrK's user avatar
  • 305
6 votes
4 answers
525 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 ...
Mark Jones Jr.'s user avatar
6 votes
1 answer
12k 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 $c_{D0}$?
Robe's user avatar
  • 618
6 votes
1 answer
12k 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 ...
VladBlanshey's user avatar
6 votes
1 answer
954 views

Why is this chart called a Short Field Effort Takeoff Ground Roll and not simply a Short Field Takeoff Ground Roll?

What does the word 'effort' mean in this context?
jskypilot's user avatar
  • 3,829
5 votes
2 answers
970 views

Can the energy dissipated in a power-off descent be calculated and expressed in horsepower?

If the weight in pounds of an aircraft is known along with its sink rate in feet per minute at best power-off glide conditions, can the horsepower being dissipated by drag as the plane descends via ...
niels nielsen's user avatar
5 votes
5 answers
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.
User's user avatar
  • 163
5 votes
4 answers
738 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 ...
summerrain's user avatar
  • 3,474
5 votes
3 answers
2k 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 ...
Tomas's user avatar
  • 91
5 votes
9 answers
15k 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 ...
summerrain's user avatar
  • 3,474
5 votes
1 answer
11k 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?
Gary Zenger's user avatar
5 votes
2 answers
2k 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 ...
Lenny Vogt's user avatar
5 votes
5 answers
3k 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: ...
Andrew De Forest's user avatar
5 votes
1 answer
715 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 ...
Aurelius's user avatar
  • 151
4 votes
2 answers
3k views

Help me understand the A220-100 takeoff chart

Here is the takeoff performance chart of the Airbus A220 (CS100). According to Wikipedia, the MTOW runway length needed is 1500 metres. However, this chart seems to suggest that a runway length of ...
Knathuul's user avatar
  • 225
4 votes
2 answers
843 views

What are the standard numbers for fuel consumption (kg), kg/NM, and kg/h, of Boeing 737-300?

I'm currently working on a school project regarding the analysis of Boeing 737-300 fuel consumption. I'm working on some parameters that my supervisor gave me, which are : Total fuel consumption (kg),...
Luthfi Ahmad's user avatar
4 votes
1 answer
1k views

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 ...
richpiana's user avatar
  • 297