# Questions tagged [aircraft-performance]

Aircraft performance covers areas such as the amount of runway required to takeoff or land and how fast an airplane can climb or descend.

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### Why Lift-induced Thrust Required(Tr) decreases and Zero-Lift Tr increases with the increase of velocity?

As the minimum Tr is at the point where L/D (lift/drag) ratio is the most. And Lift-induced Tr depends on the Coefficient of Lift, (Cl)^2 and Dynamic Pressure (q) which also increases as velocity ...
389 views

### What is causing these “corners” on this F-104 V-n diagram?

In this V-n diagram for an F-104 (source: this Wikipedia link), on the left-hand edge of the flight envelope, what is causing the "corners" that we see at the following points? (Numbers are ...
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### In this F-104 V-n diagram, why does the stall speed (in terms of IAS) decrease with altitude in some parts of the flight envelope?

(This question has been edited to reflect a change in perspective: based on answers to the related question What is causing these "corners" on this F-104 V-n diagram?, I now believe that the ...
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### For a supersonic inlet, does an increase in Mach number lead to an increase in adverse pressure gradients?

For a supersonic inlet, does an increase in Mach number lead to an increase in adverse pressure gradients because of the shock waves(which leads to boundary layer separations) and decrease in inlet ...
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### What propeller size should I use for my ultralight trike [closed]

I'm using a 15hp engine 2500rpm
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### How do I calculate the centre of gravity on the lateral (transverse) y-axis?

I have a real issue with determining the centre of gravity for the y axis of an aircraft, especially with selecting the reference/datum point and how to measure the displacement. Please I would really ...
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### What effect does a direct crosswind have on takeoff performance?

Is the take-off distance increased by a direct crosswind?
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### How are take-off segments defined?

From take-off performance calculations I remember that the take-off and initial climb was expressed in a number of segments. Each segment had its own performance requirements. I presume they are ...
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### Aircraft thrust calculation

I had a question regarding thrust calculation for an aircraft during cruise. For an aircraft flying at a constant cruise altitude and a constant Mach number (level unaccelerated flight), what exactly ...
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### What happens to Vyse and Vxse above the OEI ceiling?

An EASA ATPL question/answer insists, counterintuitively, that a twin which loses an engine and must drift down will find its least rate of sink at Vxse. I've been trying to understand this, but haven'...
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### Will my CRI CRI twin engine plane fly if I replace the engine with a single 15hp gasoline engine? [closed]

I'm using a lighter materials to rebuild plane, to cut down plane weight to 56kg and a 1.2m 3blades propeller.
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### In which part of the flight does a plane reach maximum lift?

In which part of the flight does a plane reach maximum lift? My logic: I think a plane reach maximum lift in a horizontal flight, when a plane start rolling on a runway, landing gear produce more ...
111 views

### Optimizing the airplane for best cruising altitude and velocity

In the conceptual phase of the design, I am optimizing various entities of an airplane for the best cruising altitude and speed to reduce the cost, which also includes MTOW and fuel weight. Consider a ...
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### How does deploying flaps change the gradient and rate of descent?

My understanding is: Using the gradient formula "(T-D)/W x 100", we can see that with the deployment of flaps, the gradient would reduce (due to the drag added). And since Rate of Descent (...
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### What is the fuel burn rate for climb of a C-130J Hercules?

I am trying to graph the payload range for a C-130J Hercules and I need an approximate value for fuel burn rate which I cannot seem to find online. Does anyone know approximately how much fuel a C-...
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### Ceiling parameter Derivation

I read the absolute ceiling of an adequately powered airplane is determined by the formula, $\frac{W}{S} = \frac{1.4}{2} p M^2 CL$ Where, $W/S =$ Wing Loading $M =$ Mach Number $CL =$ Lift Coefficient ...
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### Do manufactures list the maximum speed of an aircraft based on its theoretical maximum speed or dive speed?

I know that the absolute maximum velocity of an aircraft is based on the thrust available. However the aircraft is usually limited beforehand by other speed limits such as dive speed and Mach Never ...
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### Descent of Light attack aircraft to loiter altitude

How do Light Attack Aircraft (LAA) such as the Embraer Super Tucano descend from their cruise altitude to their loiter altitude to be on-station above ground troops? I want to know the way these ...
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### What thrust is used for thrust to weight ratio?

Performing some preliminary calculations for an aircraft design I have and was wondering what thrust I should use to calculate thrust to weight? The thrust calculations I have, vary due to speed (...
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### Are there certification requirements for an emergency descent?

In case of emergency, an aircraft may have to descend very quickly. Is there some performance (L/D ratio with full spoilers, descent rate, ...) to be proven in the certification process for such ...
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### Can I derive the wind speed and direction? [duplicate]

If I know the IAS and GS (with directional components) of an aircraft, can I derive the wind speed and direction? I'm working on an application that simulates the flight of an aircraft. Another ...
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### What should be the thrust weight ratio for takeoff? [closed]

I am doing some calculations for preliminary design of an airplane and I was wondering how I would go about determining the minimum thrust to weight ratio needed for the aircraft to takeoff. Which ...
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### CL604/650 (or CRJ1/2) max loiter time (using it as a reference point to compare the A-10 to)

In some discussions I was having with a (back-office) USAF acquaintance about the F-35 vs. A-10 debate, the topic of loiter time came up. Wikipedia provides a 1.88 hour (112min) loiter time for the A-...
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### 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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### Why are older airplanes still in use?

It is normal to see older planes (20+ years) quite frequently. In fact, a few months ago I saw a plane over 50 years old (not in a museum but on a runway, about to take off). Comparing to cars, there ...
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### What happens if I am flying at a higher Lift/Drag ratio than required?

I created for me a table from an aircraft for Mach=0.8 for alpha= 0° to 8° Actually, I an alpha of alpha=4° should be sufficient, so that my lift coefficient is enough, to counterbalance the weight in ...
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### Can a plane with a thrust-to-weight ratio less than one fly vertically and perform loops?

In the game Battlefield 1 you can fly a Sopwith Camel vertically and perform different kinds of aerobatic maneuvers like loops. According to its specifications, its thrust-to-weight ratio should be ...
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### Why doesn't temperature affect Pressure Altitude?

In this picture: it states the tops and bottoms of the 3 columns of air have the same pressure. This explains the error in altitude indications given in a non-standard temperature. Pressure only ...
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### How to calculate the minimum possible flight speed of an aircraft?

So for the minimum possible flight speed an aircraft can fly with for a given altitude, I just use Lift=Weight and solve for the velocity. But: I need to insert a lift coefficient, which I can get ...
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### Why is there no lift component when calculating rate of climb?

I read this post about how to calculate the rate of climb How does climb-rate vary with density/pressure altitude? So in the image, all the forces are drawn. I am wondering, why the rate of climb does ...
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### Fly a fixed wing single propeller airplane like a helicopter?

Has anyone tried to "helicopter" an airplane? And succeeded? And posted this video on the internet where I can find it? What I'm talking about with what I would call a "helicopter&...
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### What is the correct range of the 787-10?

There are two conflicting values for the 787-10's range; they are: 6,345 NM (11,750 km) -- boeing.com 7,000 NM (12,975 km) -- on the same website few years ago, as well as flightglobal.com Note: In ...
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### Relationship between Load-Factor AND Gliding Ratio

I am wondering about the g-load and its relation to the so called gliding ratio. I read this really good contribution here on this forum: Does lift equal weight in a climb? So the g load factor is ...
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### What is the effect of thrust vectoring effect on the rate of turn?

I just got a question after reading my old Principles of Flight book. The equation for the rate of turn is $\textrm{ROT} = 1,091 \cdot \frac{\tan(\phi)}{V}$, with $\phi$ denoting bank angle and $V$ ...
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### What examples are there of top-mounted engine motor gliders?

I would like to know which motor gliders are there with regards to the following criteria: Top-mounted engine stowable landing gear great L/D ratio high maximum g-load at least 180kg usable weight? ...
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### When the F16 is landing the AOA will be at 11 degrees, but speed modulates more. How is possible to have fixed AOA but not the speed?

The speed in landing pattern is not fixed one due to the weight/drag of the aircraft at the moment(loads of bombs and fuel). But if you speed up then you're going to go upwards don't you(if you keep ...
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### What is the maximum side slip angle that can be achieved by a F-16?

During which flight regime is maximum side slip needed (apart from take-off and landings in cross winds)? I have learned that during a knife edge maneuver, the side slip angle plays a crucial role in ...
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### Explained intuitively, why does aspect ratio affect induced drag?

Over the last few hours, I've been trying to intuitively understand induced drag, and how aspect ratio affects it. I already know the equations, but while they explain the relationship, they do not ...
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### How to compute thrust to weight ratio of a Cessna 172?

Cessna 172 has weight about 1 ton and it's engine produces about 213 Kg of thrust, and it flies great. So if I make a plane with a weight of 100kg including pilot and fuel so will 15 kg thrust good ...
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### How can an aircraft hover almost vertically?

(Source: https://fat.gfycat.com/) The aircraft in this GIF (although being an RC plane) seems to be flying vertically, just meters above the ground. How is this possible? How is it possible to control ...
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### Question about the difficulty of a couple of airplane maneuvers [closed]

I have a hypothetical scenario and I was wondering if any experts might be able to speak to it. I will lay out the scenario, with a couple of specific questions, and maybe some honest answers will ...
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### Why do most single propellers have a clockwise rotation?

Why do most single propellers have a clockwise rotation (seen from the pilot's point of view)? There are though multi-engine planes that have each propeller rotating different directions, but in the ...
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### Why did Concorde have a 8000 ft airport elevation limit?

According to the Concorde Flying Manual Volume II(a) - 1 Operating Limitations - page 01.01.02 the take-off and landing airfield altitude is minimum -1000 ft and maximum 8000 ft. Why is Concorde ...
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### Why is the maximum endurance for a piston aircraft at sea level?

The Canadian Flight Training Manual stated this when talking about maximum endurance: For reciprocating engines, maximum endurance is achieved at sea level. The book does not explain further as to ...
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### Which “Power Available” graph is more correct?

Trying to understand the drag and power required/available graphs for a piston + propeller airplane. Both graphs are from current book/website and while they are showing mostly the same thing, I ...
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### Downwind Myth Question

I was reading a discussion about the "Downwind Myth" and a doubt arose: If we are taking off with a 50knots headwind, that wind component will be part of our dynamic pressure, and so in that ...
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### How can I calculate the fuel consumption of an Airbus 320-200 at various loads?

I want to know: What is the fuel consumption of an Airbus A320-200 - 180 Seats, at 100% load factor for a distance of 2000 km? What is the fuel consumption of an Airbus A320-200 - 180 Seats, at 80% ...
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### Was the P-82 twin Mustang better than the P-51D? [closed]

The P-82 twin Mustang was made to replace the P-51D in the escort role. It was faster, and had two engines with two pilots. It also had a better armament but wasn't as maneuverable as the P-51D. Which ...