# Questions tagged [thrust]

Questions about the propulsive force of a powered aircraft.

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### In a straight and level flight if thrust is equal to drag how is aircraft moving forward?

If two forces are equal and acting in opposite direction should not the object remain stationary. Is there an excess thrust which actually pushes the aircraft forward ?
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### What could have been done better in United Airlines Flight 232 when differential thrust was used?

In United Airlines Flight 232, on their DC-10, all hydraulic fluid and pressure was lost on all three systems, simultaneously. Fitch, who was a training check airman on the DC-10 was on board and ...
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### How can the wing generate more lift than the thrust? [duplicate]

I recently checked about the max takeoff weight of an A380 and the thrust it can provide at TO/GA power and I was quite shocked by the results. The total thrust by the engines was only about 127000 ...
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### How can I cross verify my propeller thrust? [duplicate]

I'm simulating a propeller in Ansys and im getting a thrust of 2000N. The forward speed is 85m/s and 240.25 rad/s angular velocity and the diameter of the propeller is 1.8m. Since I'm not able to find ...
1 vote
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### What is the mathematical relationship between mass and speed for constant thrust in level fight?

Imagine that we have a wing with constant thrust in level flight. Then imagine that we add mass to that wing. In order to maintain level flight, I would expect that the angle of attack would need to ...
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### Does propeller width have a material impact on thrust? [closed]

I have seen propeller thrust calculations and they do not appear to have the variable of propeller width. They only use diameter or radius. What if any impact does width of the propeller have? Here is ...
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### IDLE Factor determination

The Flight Management System (FMS) utilises the Idle Factor to modify the computation of the vertical profile whilst descending. During this phase, the FMS calculates the vertical profile and ...
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### A transfer function relating jet engine thrust to pitch angle during a phugoid motion

Crossposted on Mathematics SE I am doing a school project that requires me to find a transfer function that relates the thrust of a jet engine (which could change with time in one way or another) and ...
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### Are UDF/Propfan Engines Thrust Producing or Power Producing? [duplicate]

For the purposes of aircraft performance (best endurance/range speeds, Vx, Vy, etc.) would a propfan be considered a power producing engine or a thrust producing engine? I would imagine it would be ...
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### What determines maximum speed of a propeller aircraft - Thrust or Power?

I'm reviewing training materials1 for straight and level flight. The content focuses on drag types and explains that the required thrust curve is equivalent to the total drag curve. It then introduces ...
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### Can you augment turbofan thrust using steam injected into the bypass?

Would using waste heat from the core exhaust to turn water into steam increase takeoff thrust when injected into the bypass before/aft of the fan? If so, which would be better? Could this possibly ...
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### How do "thrust rating limits" work on the A320?

On page 11 of this A320 FCOM (power plant section only), a "thrust rating limit" mechanism is described. However, it doesn't go into much detail, and I could find little other information ...
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### What is the maximum speed at which thrust vectoring can be used? Thrust Vectoring on the SR-71

The SR-71 is limited to a 45 degree bank turn at speeds in between mach 2.85 to ~3.2. This means the blackbird would take almost 5 1/2 minutes to make a 180 degree turn at mach 3. Would it be possible ...
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### What are the common sensors/ways that reverse thrust is measured for turbines?

I am looking for a sensor to measure reverse thrust on a small hobby turbine engine, a jetcat p100-rx. I did not find clear ways industry measures reverse thrust from previous searches online and was ...
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### Why does thrust differ in different reference frames?

If a jet engine flies with 4 m/s in the air and we want to calculate thrust for two different reference frames, can we prove that the calculated thrust for both reference frames are equal to each ...
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### Why do we take into consideration holes for pressure thrust in jet engine calculations?

In many sources related to jet engine thrust calculations such as https://www.jet-x.org/a8.html , pressure thrust of a module such as combustion chamber, nozzle or compressor, is calculated by front ...
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### Is contact between flow and inner walls of nozzle required for thrust generation?

I uploaded a picture below explaining over-expanded flow/nozzle condition with regards to thrust. This aviation source tells that “extra nozzle walls don’t generate any additional thrust because flow ...
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### If a jetliner is giving TOGA thrust but never releases the (parking) brake, will the brakes heat up?

From my - admittedly - limited knowledge of physics, the energy generated from the engines needs to go somewhere; will it go into the brakes or does it just dissipate into the air?
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1 vote
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### optimal airplane propeller placement along the vertical axis?

is there a guideline for optimizing flight based on where the engine/propeller is placed along the vertical axis? some planes have the propellers well below the wings, some on the wings, some above ...
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### Where is the thrust of a turbojet felt? [duplicate]

At a high level, this is simple. Hot gas goes out the back, and Newton's third law says the engine is pushed forwards. But when you look inside the engine, it's less clear which part experiences the ...
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### How to determine thrust and power requirements from take-off ground roll distance?

I'm working on a project which requires me to determine the power requirements of a propulsion system from a specific take-off distance. Starting with this equation:  s_g\approx \frac{1.21(W/S)}{...
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### How does a fan in a turbofan engine suck air in?

I watched lots of video related to sucking process of a fan in a turbofan engine, but I'm confused at a point. In this link and many videos like this, I found the fan'...
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### Helicopter total power required: zero wind speed while climbing --vs-- down wind speed while hovering

I've been stumped on this for a while. Let's say you have a helicopter in climb mode (i.e., 100 ft/min) with zero wind speed present. Would the total power requirement be the same as if the helicopter ...
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### How can I calculate the thrust of a propeller?

I am working on designing a paramotor, and need to calculate estimated thrust for the propeller. Is there a calculator or equation where I can input a diameter, pitch and rpm and get a ballpark thrust ...
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### If the pitch of a bypass fan blade in a turbofan is fixed how does it manage to provide thrust over such a large speed range?

A fixed pitch propeller is only good for aircraft that do around 100kts because the angle of attack on the propeller decreases as the forward airspeed of the aircraft increases, limiting the thrust ...
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### Would the dle 55ra engine be enough to power my paramotor(ducted fan)?

I plan on using the dle 55ra engine to produce 5hp at 8,500 rpm. I am using it in a paramotor, and to save space I am considering using a ducted propeller similar to the Fulcrum power pod. The duct ...
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### How much horsepower do I need for my paramotor?

Assuming my full kit and I weigh 82kg total, I have estimated that I need 5hp. To calculate this, I used the formula: weight force (W) is F = m g W= 82kg*9.8 ms/2 =401.8 Newtons Now, if the drag ratio ...
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### How much thrust should be applied when you set the autopilot to a specific altitude?

After a plane takes off the pilot usually sets the autopilot to the altitude of the flight level they are about to cruise at, e.g. 30,000 ft, right? When that is the case, how much thrust should be ...
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### how does the lilium jet counter asymmetric thrust?

So Lilium states that its jet is a tailless design. Now, you can see that it has engines on both sides of the centerline. Lets imagine that all of the engines on one side fail, how does it counter ...
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### How can I calculate the TOTAL drag of the ENTIRE airplane?

I have an aircraft similar to a Cessna 172 and am using a virtual wind tunnel software (flowdesign) to get a drag estimate. I import the airplanes 3D model and I get around 2240 lbs of drag with a ...
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### How do airplanes with thrust lines above CG still fly without a down pitch moment?

Mainly the Icon A5. I remember trying to make an RC aircraft similar to it, but the moment i'd spin up the motors the aircraft would understandably pitch down. i couldnt fly it at all. So how do these ...
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### What is the general mathematical relationship between increasing an airplane's weight and the needed thrust to fly?

I understand that increasing an aircraft's weight without changing any other properties means that its takeoff, stall and cruising speeds all increase since you need to generate additional lift. So ...
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### How much thrust can a balloon generate with wings?

I have heard that some balloons have been made with wings, angled such that they generate some forward thrust during the ascent. Balloons can also theoretically generate thrust with wings during a ...
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### How can a turbofan's fan generate thrust in cruising flight if air is being slowed down?

High bypass turbofans in airliners generate most of their thrust from their fans, not their "cores". However, at cruise they are actually spilling some air past the intake rather than ...
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### What is the thrust to weight ratio of the A330-900neo?

Does anyone know what the thrust-to-weight ratio is for the Airbus A330-900neo? I'm getting different numbers when I try to calculate this for myself.
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### static thrust vs. prop RPM data?

edit: question was too long, and is actually simple, so I removed unneccesary description Background: There are many questions here about: propeller efficiency changes to thrust when it is dynamic ...
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### Why is the Cirrus Vision SF50's turbine angle so acute?

I saw a Cirrus Jet on the ramp and was struck by how much its engine points upwards. I can't recall having seen this kind of positive thrust angle, and so wondered what the explanation was. A picture ...
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### Why the greater the propeller slip is, the more thrust it generates?

Forgive my poor English skill and my entry-level understanding of aviation stuffs. I'm currently a student pilot. As I understood, the propeller slip kind of represents the propeller efficiency in ...
1 vote
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### How is bleed air flow related to thrust level?

I read that the bleed flow negatively affects the thrust levels for a turbofan engine. However, I was wondering if vice-versa is true as well? Whenever the thrust levels for a turbofan are lowered at ...
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### Power calculation of propeller

This is probably a very simple question, but I have been really struggling and need your help. I have simulated a propeller with these parameters on Ansys: Thrust: 2000 N Angular Velocity: 314 rad/s ...
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### Why do turboprops not have a thrust value in the specifications? [duplicate]

When looking through aircraft engine specifications, turbofans always provide a thrust value, e.g. in JT8D engine: https://prattwhitney.com/products-and-services/products/commercial-engines/jt8d In ...
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### Why is thrust (in a high bypass turbofan for e.g.) non-linear with respect to N1?

I've been studying jet engines for a short while now and I think I have a pretty decent understanding of how thrust is generated, but one thing I'm struggling a bit with is how thrust varies across ...
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### What is meant by the pointing vector and pointing vector magnitude in ECI?

In Siouris's Missile Guidance and Control Systems, it is stated that the angle of attack can be approximated in a 3DoF (degrees of freedom) simulation by the following equation: I know that ECI ...
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### Why do pilots slowly give the plane more thrust during takeoff?

I have mostly seen pilots slowly pushing the throttle to toga during takeoff. But why? Why don't they just directly put the throttle to toga? Wouldn't that save runway length?
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### What is the maximum Mach number that can be achieved at the exit of CD nozzle?

I understand that you can get Mach 1 at the throat of a convergent-divergent (CD) nozzle and after that you can have two roots, one is for subsonic and other is for supersonic. Considering the ...
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### What do you call a fall that is due to too little engine power, not due to cessation of aerodynamic lift?

If you raise your plane's pitch but the engines can no longer counter the gravity and you begin to fall (because the engines are too weak, not because of too little lift), what do you call that? This ...
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### Is axial bearing in turbo fan,turbo jet engines neutraly loaded?

Is axial bearing in turbo fan,turbo jet engines neutraly loaded,if yes then turbine/fan and compresor produce eqaul and opposite force? If yes ,where then thrust come from,at internal walls,must be ...
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### What exactly is the pressure thrust component and why does it exist?

I'm teaching PowerPlants on a ATPL theory course and honestly have some trouble wrapping my head around this one: Most literature describes the term "pressure thrust" – as opposed to "...
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### Using a spring balance to find static EDF Thrust

I have been attempting to measure the static thrust of my EDF with a spring balance. It is part of a group university project. The EDF specs are as follows: 90mm freewing 9 blade 1900 Kv thats rated ...
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