Questions tagged [thrust]

Questions about the propulsive force of a powered aircraft.

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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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0 votes
1 answer
209 views

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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9 votes
5 answers
2k views

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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2 answers
151 views

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 ...
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1 vote
1 answer
115 views

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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3 votes
3 answers
380 views

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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7 votes
2 answers
3k views

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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3 votes
0 answers
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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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1 vote
1 answer
79 views

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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18 votes
7 answers
6k views

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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2 votes
1 answer
187 views

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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2 votes
5 answers
419 views

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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1 vote
1 answer
100 views

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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10 votes
3 answers
944 views

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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4 votes
2 answers
75 views

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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16 votes
5 answers
3k views

Why is thrust inverse to speed in piston engines?

It is said that piston engines have constant power output, and thus their thrust is inverse to speed (e.g. here), while turbines have relatively constant thrust. I'm looking for an intuitive ...
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4 votes
2 answers
510 views

How to calculate the efficiency of a rubber powered propeller

I made a simple test rig together with a stopwatch to measure the thrust (in grams) with respect to time of a rubber powered propeller. This enabled me to compare the performance of different ...
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1 vote
0 answers
159 views

What is the specific fuel consumption and cruise thrust of PW1521G engines?

I'm looking for the specific fuel consumption (SFC) and thrust related to PW1521G in cruise regime, as well as the associated assumptions for these ratings. I can't find them online.
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0 votes
1 answer
350 views

Electric ducted fan with thrust tube thrust and exit velocity calculation

I am working on an electric ducted fan rocket that has thrust vector control,in image 1. The 90mm EDF is located abit higher above this blue section, near 1., so I believe the blue section becomes a ''...
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3 votes
1 answer
498 views

Is thrust larger than weight in a vertical climb?

Image source Very much related to the many questions and great answers to lift and weight in a climb - if an F-16 climbs vertically at a constant speed, is thrust greater than weight?
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1 vote
0 answers
247 views

Calculating the Thrust vs RPM Relationship of a Brushless DC Motor

hope everyone is doing okay. I am conducting a project with my friends for an Unmanned Aerial Vehicle. We are first using MATLAB - Simulink to design and simulate the quadrotor. We completed the ...
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2 votes
1 answer
401 views

Other than fighters, which airplanes can fly straight up?

I would think, for example, all modern fighter jets can maintain 90 degree climbs due to having thrust to weight ratio greater than one. Are there any other air planes which can do that?
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0 votes
0 answers
73 views

Can a stopway withstand thrust of B737 engines on takeoff if the aircraft is lined up on the edge of the runway?

Can the thrust of Boeing 737-300 engines break the asphalt surface of a stopway marked with yellow chevrons? Can anyone give a documented reference?
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3 votes
1 answer
295 views

What is the approximate thrust at sea level for a C-130J Hercules?

I am looking for the approximate thrust of a C-130J Hercules under ISA sea level conditions. Also the efficiency of its propeller would be of help. An answer to this question would really help my ...
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1 vote
2 answers
373 views

On a Boeing 737, can the APU, BY ITSELF, provide enough thrust to move the plane while on the ground? [duplicate]

There are numerous questions and answers about the ability of an APU to provide enough thrust to maintain flight. In contrast, my question is whether the APU, by itself, provides enough thrust to ...
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0 votes
1 answer
110 views

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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3 votes
2 answers
349 views

Relation between lift force and torque produced in propeller used for vertical take-off and landing aircrafts

There are many answers for this question but none of them are specific. I need to find the exact relation between the lift force of a propeller of specific pitch, attack angle , dimensions and ...
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-3 votes
1 answer
186 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 ...
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3 votes
2 answers
837 views

Why is TOGA thrust 'never' 100% N1?

The title is voluntarily the opposite of this question: Why isn´t TOGA thrust always 100% N1 or N2?. I explain to you with an example: I'm looking to the FCOM of an A320 which states that the "...
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1 vote
1 answer
442 views

What is the difference between RTOP, MTOP, and MCP?

I am currently learning how to fly the SD3-60 (Shorts) Aircraft, and I am trying to gain an understanding of RTOP (reserved take off power), MTOP (max take off power), and MCP (max continuous power). ...
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0 votes
3 answers
244 views

Why do we take off with maximum power settings?

In most GA prop airplanes, take-off is executed with full throttle and high rpm. The usual reasoning is that this way, we leave the first few hundred feet, where failures are most severe, behind as ...
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1 vote
2 answers
147 views

This concerns the GE90X fanjet engine which generates 130,000 LBS of thrust at takeoff [duplicate]

This concerns the GE90X fanjet engine which generates 130,000 LBS of thrust at takeoff. But for this example the engine is secured to a test mount, and under "full throttle", the thrust ...
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  • 11
1 vote
0 answers
41 views

How to calculate turbojet thrust at variable altitudes and mach numbers?

I am interested in developing a flight model in jbsim. jbsim requires a thrust table similar to as follows, with varying mach and altitude numbers (with thrust as a fraction of max): ...
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1 vote
2 answers
265 views

How much thrust is required for a Boeing 747 to "keep flying" at 4 km altitude?

Not full power, just enough to keep the plane moving at 4km altitude.
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2 votes
6 answers
736 views

Why can't you have sail-powered airplanes?

So, sailing boats take the kinetic energy of a crosswind and turn it into thrust by using their sails as lifting surfaces, and the discussion I had in the comment section of this question made me ...
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0 votes
2 answers
133 views

Can thrust be produced only using the forward speed of a nozzle?

Why can't a nozzle that is already in relative motion to the air produce thrust by speeding up the air that passes through inside it? So let's pretend you're in a glider with two converging nozzles (...
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1 vote
2 answers
401 views

Is Assumed Temperature used in conjunction with a Derate in the B737 NG?

When using an Assumed Temperature for Takeoff, is it common operational practice to also use a Derate?
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0 votes
2 answers
221 views

How does the aircraft keeps propelling forward when airflow and thrust are not aligned?

Assume an aircraft is flying at an angle of attack of 10 degrees, and that the incidence angle between the aircraft fuselage and the wing as well as the angle between the wing and the engine mount is ...
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0 votes
2 answers
278 views

What´s the logic behind the Power Curve?

Aircaft thrust is what counteracts drag, but in flight school they tought us that propeller aircraft are "power producers" and not thrust producers as jets. (That´s because the propeller ...
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1 vote
1 answer
2k views

How do power and thrust curves compare?

I would like to really understand why when talking about jets we care about thrust but when talking about propeller aircraft we care about power. (THRUST)="Just a force" (POWER)= work/time = ...
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4 votes
1 answer
437 views

Is Flight Idle a constant?

Is "Flight Idle" for a jet engine a constant N1% value or does it vary with Altitude, and OAT?
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0 votes
1 answer
507 views

Should "Thrust Reduction" and "Acceleration" heights be the same for the Boeing 737 NG?

Should the Thrust Reduction height be the same, lower or higher than the Acceleration Height? In other words, what is their "correct" sequence. I am referring specifically to the B737NG, if ...
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0 votes
2 answers
398 views

Is this the relationship between rpm and thrust of a Turbofan? [duplicate]

In this graph from the FAA Airplane Handbook Chapter 15, page 5: It looks like it is talking about "jet engines" but is it engine type specific or it is for both turbojet/fan/prop/shaft? It ...
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1 vote
2 answers
610 views

Why would sea level static thrust have a takeoff and a maximum continuous value?

In the type certificate data sheet for a jet engine, there is this table static thrust is the thrust generated by the engine when the plane is at rest with respect to the Earth and the surrounding ...
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  • 315
5 votes
1 answer
689 views

Why is thrust said to be constant over speed for a jet engine?

I'm just interested in some basic facts regarding flight. On reading the rather "low level" book "Understanding Flight, David F. Anderson, Scott Eberhardt), I recently came up to the ...
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3 votes
2 answers
178 views

Is the well known textbook-formula for net-thrust oversimplified or do I have a misinterpretation?

In order to understand how Jet-Engines works I came across the "famous" formula for net-thrust: https://en.wikipedia.org/wiki/Turbojet#Net_thrust $F_{thrust} = Q_{out} \cdot v_{out} - Q_{in}\...
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  • 241
1 vote
1 answer
227 views

How can a small ducted fan produce a large amount of thrust?

This 15.2 cm ducted fan by Schuebeler can produce 175 Newtons of static thrust. How is this possible in such a small diameter? If this seems normal, then why and how can this ducted fan produce that ...
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2 votes
2 answers
405 views

How does altitude affect the TAS and thrust of an electric fan powered aircraft?

I'm confused about the relation between IAS, TAS, thrust, and shaft power, for an electric application. Yes, higher air is thinner, and thrust goes down due to higher airspeed. What I've researched ...
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1 vote
1 answer
220 views

How can I calculate the minimum thrust to weight ratio required for a given takeoff distance?

I am building a plane and I have a take-off distance of 50ft, is there a way for me to estimate the thrust-to-weight ratio required for this constraint (even if it was in terms of say wing loading)?
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0 votes
2 answers
146 views

Can I check my density altitude with brake tension?

The same way one would apply the brake and accelerator, the more torque the more break is needed to hold the car, can a plane use this same technique to check the plane thrust and air density before ...
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