Questions tagged [performance-calculation]

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

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0 answers
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Why does V2 decrease for intersection takeoff

I have noticed that the VR and V2 decreases for same FLEX when departing from an intersection runway even when sufficient stop margin is available. What is the reason for this? And also does EFB ...
-1 votes
0 answers
94 views

Airfoils and materials used in horizontal stabilizers

I have to do a research project on the weight optimization of a Horizontal Stabilizer through the use of composites. I am struggling to find information about what kind of airfoils are generally used ...
3 votes
1 answer
130 views

How useful were the wings and tail of Jean-Pierre Blanchard's balloon?

In 1784, Jean-Pierre Blanchard fitted a hand-powered propeller to a balloon, the first recorded means of propulsion carried aloft. In 1785, he crossed the English Channel in a balloon equipped with ...
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Are there significant differences between EASA and FAA when teaching jet aircraft performance?

Both regulatory bodies did a great effort in regulation harmonization, but I'm looking for any significant differences (if any) in how is taught the subject from the pilot point of view, i.e. ...
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4 votes
1 answer
230 views

Calculating airspeed by flying in a U shape: Horseshoe Heading Technique

I saw some equation in a log recently and I believe it went something as follows: $v_1$ : flying North, $\ \ v_2$ : flying West, $\ \ v_3$ : flying South. $$ \text{TAS} = \frac 1 2 \sqrt{v_1^2+v_2^2+...
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3 votes
3 answers
232 views

Do pilots of piston/prop aircraft have discretion to determine how much runway is required for an intersection departure?

For piston/prop aircraft requesting intersection departure, is it pilot discretion for the minimum amount of runway length required? Is there a takeoff calculator in conjunction with calculations?
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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 ...
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3 votes
1 answer
143 views

Takeoff distances published in OEM manuals

Background For academic research purposes, I have developed a first-principle takeoff performance model that returns a takeoff distance required (TODR) based on the aircraft type (incl. its associated ...
1 vote
1 answer
80 views

How to read performance chart? [duplicate]

From the Flight Planning and Performance quiz for PPL, there is a question asking to calculate the distance needed for landing over 50ft barrier. According to the example shown by the manufacturer (...
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2 votes
1 answer
261 views

Why is maximum zero fuel mass used in take off mass calculation?

In calculation we consider maximum takeoff weight , maximum landing weight and maximum zero fuel weight we selected the lowest of below mentioned Maximum Zero fuel weight + Take off fuel Regulated ...
4 votes
1 answer
285 views

Is there a way to calculate the braking distance for a light aircraft?

PPL student, I train in a C152. Reviewing its POH I cannot find a method to estimate brake performance roll (as I would do with T/O roll). Is there any method or rule to calculate brake roll in ...
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8 votes
1 answer
417 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 ...
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11 votes
4 answers
3k 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.
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5 votes
2 answers
952 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 ...
8 votes
1 answer
767 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?
0 votes
0 answers
108 views

I don't quite understand the derivative in this vertical wind gust formula

First my english writing skill is still bad so pardon me if i accidentally made any mistake TT-TT. So recently I have learnt about how the vertical gust affect the load factor and the calculation ...
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 ...
0 votes
0 answers
69 views

Is a ducted fan considered a jet or propeller for the performance parameters?

Right now I am working on a UAV design which will use ducted fan. But the performance calculations are a bit troublesome. For some calculations jet and propeller results are almost same but for the ...
-2 votes
1 answer
209 views

Should a runway overrun be expected if takeoff is begun with one-engine-out?

Multi-engine aircraft have enough power to successfully takeoff if one engine fails after V1. But what if, on a runway equal to the specified takeoff distance, someone decided to roll with one engine ...
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7 votes
1 answer
422 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 ...
1 vote
3 answers
168 views

What power have I obtained?

I am currently working on a question in aeronautical engineering. The question has asked me to provide the available power. I have calculated the drag, and am given the constant velocity. With that, I ...
4 votes
2 answers
180 views

Are there more refined rules-of-thumb for Top of Descent calculation, than the simple FL x 3?

Forgetting the excellent capabilities of VNAV for a moment and reverting to simpler days, is there a rule of thumb to further refine the FL x 3 rule for Top of Descent calculation, when there are ...
7 votes
3 answers
760 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 ...
2 votes
0 answers
61 views

Slotted wing loading and structural analysis

I'm trying to determine moments and forces on a wing with a fixed leading edge slot (trying to verify the Ragwing RW19 wing before starting the project). It's quite straightforward for a non-slotted ...
1 vote
1 answer
302 views

How to calculate TAS and fuel for Diamond DA20-C1?

The PoH for the Diamond DA20-C1 is here: http://support.diamond-air.at/fileadmin/uploads/Canada/Tech_Pubs_DA20-C1/AFM/DA202-C1-Rev-28.pdf. The plane has an MT prop, and the supplement for it is here: ...
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1 vote
1 answer
87 views

What are the best methods for calculating lift during different stages of flight?

Supposing I have the all dimensions of an RC airplane: wingspan, NACA airfoil, aspect ratio, fuselage length, etc., what would be the best methods of calculating the expected lift the aircraft should ...
0 votes
1 answer
74 views

Replacing or supplementing turbofan with electric fan [duplicate]

Could you replace 2 B747 engines with electric turbofans? Could the 2 standard turbofans produce enough power to allow electric cruise with jets used for take off?
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4 votes
1 answer
582 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 ...
3 votes
1 answer
253 views

Is the quickest way to reverse direction by turning horizontally or vertically?

Assume my aircraft is flying with Mach 2 and I want to quickly change my direction of travel 180°. So for a horizontal turn flight I found the formula: angular velocity = g* sqrt(n²-1) / v For a ...
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0 votes
1 answer
584 views

How to calculate Night Flight time for a given flight? [duplicate]

I am currently working on a project (web app) at university to be able to calculate the amount of time spent during night flying. Currently, I have, Departure Lat and Long and Departure Time in UTC ...
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1 vote
1 answer
70 views

What units should use for velocity prediction equations?

I'm not an expert aviation but I'm designing my own RC Plane and I wanted to estimate the maximum velocity using equations (15-20) from this paper. Honestly, I am not quite sure on the units to use ...
2 votes
2 answers
521 views

Does Green Dot Speed Calculation include banking Angle?

I'm wondering, whether the Green Dot- speed calculation in the Airbus PFD does account for the actual bank angle of the aircraft. ...
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2 votes
3 answers
223 views

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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1 vote
1 answer
317 views

Have I made a calculation mistake in this ATPL question that uses the CAP 698 Chart?

I have been calculating this question but I just don't seem to get the correct answer. For this question use Performance Manual CAP 698 SEP1 Figure 2.3. Using the climb performance chart, for the ...
0 votes
1 answer
644 views

What is takeoff power? [duplicate]

I Am asking about the takeoff power here not how the aircraft takes off. What do I need if I want to calculate the power required by an aircraft to take off? What parameters should I consider?
6 votes
1 answer
604 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 ...
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2 votes
1 answer
427 views

What methods are used for calculating maximum takeoff windspeed of a helicopter?

I would like to calculate the maximum windspeed in which a helicopter may safely take off and safely land, assuming a theoretical wind environment with constant wind direction and no gusts. I ...
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9 votes
3 answers
1k 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 ...
0 votes
2 answers
261 views

Shall We Consider Reversers in performance Calculations?

Thrust reversers are featured to help slow down the plane after touchdown. Moving the thrust levers aft activates the translating cowl to open, closing the blocker doors. This action stops the fan ...
2 votes
4 answers
4k views

How is the Max Zero Fuel Weight used in calculating weight and balance?

In some weight and balance apps there is an option to "Use Max Zero Fuel Weight". Having never seen this in any of the aircraft I have experience flying, I am curious how this value is typically used ...
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1 vote
2 answers
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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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1 vote
1 answer
853 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 ...
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 ...
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5 votes
2 answers
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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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8 votes
4 answers
3k 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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0 votes
0 answers
507 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\...
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5 votes
2 answers
925 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 ...
0 votes
1 answer
1k 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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3 votes
2 answers
194 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 votes
1 answer
485 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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