# 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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### In this F-104 V-n diagram, why does the stall speed (in terms of IAS) decrease with altitude?

In this V-n diagram for an F-104 (source: this Wikipedia link), why does the stall speed at any given G-loading (in terms of IAS) decrease with altitude? The stall-speed at any altitude and G-loading ...
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### 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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### 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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### 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 ...
89 views

### 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'...
123 views

### 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 ...
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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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### 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 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 ...
2k views

### 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 (...
1k views

### 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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### 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 ...
60 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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### 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-...
128 views

### 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 ...
189 views

### 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 ...
444 views

### 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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### 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 ...
162 views

### 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 ...
144 views

### 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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### 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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### 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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### 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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### 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 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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### 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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### 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 ...
108 views

### 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 ...
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### What is the manoeuvre point?

a centre of gravity position at which stick force per g becomes zero What does this mean? If the centre of gravity happened to be at the maneouvre point, would there be stick be very light in the ...
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### Does a constant speed prop deliver max speed at max manifold pressure and max RPM?

I was reading a discussion in flight simulator forum and I found this statement: Ignoring the issue of engine overheating, max MAP and max RPM is the best thing for max speed Do you agree with that? ...
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### Why is the F-104 Starfighter’s afterburner thrust not greatly impacted by altitude?

Here is a page from the F-104 flight manual. It shows the flight envelope for the F-104 Starfighter with the powerful J79-GE-19 turbojet engine: I have a question regarding the shape of the ...
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### What is the minimum bank angle that an older aircraft like the Cessna 172 can apply in a coordinated turn?

Suppose the weather conditions are favorable and there are no significant winds. The Cessna with a speed of 200km/h starts a coordinated turn with a bank angle of 0.1° The turning radius of this ...
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### Why does “V1 increase with decreasing density”?

The statement made in the question is mentioned in one of the renowned publications. My contradictions which I have already ruled out as a potential solution: As Density decreases Vmcg decreases thus ...
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### Why is the CG envelope wider when the aircraft is heavy?

I mean, the same aircraft, but empty or on MTOW. According to MAC, those limits are the same, but the indexes are different. So if I understand that correctly, the CG can be more forward when the ...
115 views

### Why does a Thrust Vector Control System increase maneuverability?

So why can a thrust vector control system increase my maximum g-load capacity? Because still n=L/G is relevant and if I can not provide enough lift (pointing up) to counter balance the thrust (...
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### headwind, tailwind, weight, density exponents for DR400/180

I am trying to build a ground roll chart for Robin DR400/180 following the procedure described http://www.eaa1000.av.org/technicl/takeoff/topaper.htm#References. Does anyone know the tailwind, ...
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### 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 ...