Questions tagged [thrust]
Questions about the propulsive force of a powered aircraft.
119
questions
1
vote
1answer
63 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 ...
18
votes
7answers
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?
2
votes
1answer
122 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 ...
2
votes
5answers
415 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 ...
1
vote
1answer
90 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 ...
10
votes
3answers
721 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 "...
4
votes
2answers
69 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 ...
16
votes
5answers
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 ...
4
votes
2answers
467 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 ...
1
vote
0answers
119 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.
0
votes
1answer
220 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 ''...
3
votes
1answer
461 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?
1
vote
0answers
132 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 ...
2
votes
1answer
304 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?
0
votes
0answers
71 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?
3
votes
1answer
209 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 ...
1
vote
2answers
257 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 ...
0
votes
1answer
99 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 (...
3
votes
2answers
177 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 ...
0
votes
0answers
39 views
Bleed air examples and percentages [duplicate]
I'm doing an assignment in GSP where I've got to examine bleed air and it's effect on thrust and fuel consumption.
I've got to simulate 1-10% bleed air and then answer whether the drop in performance ...
-3
votes
1answer
162 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 ...
3
votes
2answers
580 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 "...
1
vote
1answer
280 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). ...
0
votes
0answers
42 views
Comparison of specific thrust vs. speed, for EDFs and propellers
I stumbled upon this graph showing the decrease in specific thrust (Thrust by Power) in relation to velocity, for a Schuebeler EDF:
https://www.researchgate.net/figure/Specific-thrust-T-P-vs-airspeed-...
0
votes
3answers
217 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 ...
1
vote
2answers
126 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 ...
1
vote
0answers
34 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):
...
1
vote
2answers
209 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.
2
votes
6answers
616 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 ...
0
votes
2answers
129 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 (...
1
vote
2answers
281 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?
0
votes
2answers
196 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 ...
0
votes
2answers
219 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 ...
1
vote
1answer
1k 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 = ...
4
votes
1answer
349 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?
0
votes
1answer
316 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 ...
0
votes
2answers
300 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 ...
1
vote
2answers
425 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 ...
5
votes
1answer
529 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 ...
3
votes
2answers
174 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}\...
1
vote
1answer
176 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 ...
2
votes
2answers
300 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 ...
1
vote
1answer
197 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)?
0
votes
2answers
145 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 ...
0
votes
1answer
124 views
Does thrust output in jet airplane remains constant when altitude increases?
I’m a noob so sorry for my ignorance. The question is: do we need (in jet airplane) to increase the throttle to maintain constant thrust output if we want to fly higher (not considering climb phase), ...
1
vote
2answers
770 views
How much thrust is produced on an A320 at takeoff and during cruise?
Where can you get the drag polar of the A320 at cruise and TakeOff?
3
votes
2answers
154 views
Can briefly explain the principle behind the inversion on this power required curve?
I’ve noticed on several graphs in the “Advanced Pilot’s Flight Manual”, that power available is lower for any given speed at 10,000 feet as compared to sea level flight. The power required curves ...
6
votes
2answers
2k views
Flex temperature isn't actually "fooling" the FADEC, right?
I'll be using Airbus terminology here because that's what I know, but I guess the concepts are universally applicable.
The way I understand flex temperature is: It's a user interface for pilots to ...
2
votes
2answers
357 views
Is it true that high-bypass engines are inherently inefficient at higher speeds?
Power consumption=Kinetic energy=$1/2mv^2$.
Thrust=momentum change=$mv$.
I keep being told that aircraft engines are most efficient when their exhaust velocity closely matches the freestream.
The ...
0
votes
3answers
243 views
Can tailwind produce reverse-thrust?
I know that the answer will probably be no, and this question might sound silly, but I wanted to think outside of the box.
If engine air intake comes from the front, and is pushed out through the ...
