Questions tagged [thrust]
Questions about the propulsive force of a powered aircraft.
90
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53 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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2answers
145 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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2answers
141 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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1answer
164 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
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1answer
138 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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1answer
75 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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2answers
81 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
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2answers
78 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 ...
2
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1answer
126 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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2answers
151 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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1answer
107 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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2answers
96 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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1answer
98 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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2answers
111 views
Can I check my density altitude with my brakes?
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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0answers
22 views
In actuator disk theory, why does changing the inertial reference frame work for Bernoulli's equation?
I was reading this website: https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node86.html, which goes over actuator disk theory, and it discusses using Bernoulli's equation in a frame of ...
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1answer
85 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), ...
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2answers
148 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?
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3answers
101 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 ...
5
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2answers
1k 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
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2answers
252 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 ...
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3answers
196 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 ...
2
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2answers
122 views
Is this plasma-thruster experiment actually measuring thrust? [closed]
This experiment, which is being presented as an initial exploration of the feasibility of using microwave-generated plasmas in a sort of electic jet engine, has been attracting some attention in the ...
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1answer
119 views
What is takeoff power? [duplicate]
I Am asking about the takeoff power here not how the aircraft takes off.
What do I need if I want to calculate the power required by an aircraft to take off?
What parameters should I consider?
2
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1answer
132 views
How much the Concorde secondary nozzle contribute to thrust?
Does anybody knows how much did secondary nozzles bucket type on the Concorde's engines contributed to the increase of thrust during take of and sub-sonic flight? This is picture of the nozzles and ...
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0answers
68 views
What is the static thrust of a Piper Arrow III?
I want to find out what's the static thrust of a Piper Arrow III (non-turbo) with Mc Cauley propeller at T/O (max) power as function of the air density.
I can't find it in the manual, I know the ...
2
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1answer
544 views
How can I calculate the relationship between propeller pitch and thrust?
I am trying to design a WWI propeller so I started calculating. The propeller comes with a specified pitch of 1.75m. The engine is supposed to run at around 1900 rpm and 147kW. These are most likely ...
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1answer
138 views
What is the takeoff thrust of a CFM56 engine?
So, to be more clear I currently have an assignment about the Boeing 737-800.
I have to find out the total takeoff distance of the aircraft. I'm using Anderson's book " Aircraft Performance and ...
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2answers
263 views
How to increase payload capacity of plane?
Keeping thrust, wing span, weight (of plane) constant, can we increase the payload capacity (nearly 50% more)? Adding payload to plane, it decreases thrust/weight ratio, how does it affect the control ...
4
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1answer
274 views
why some airplanes have their exhaust gases vectored above the wing?
I was looking at images of the SkyCourier shown below
and i have noticed the asymmetrical exhaust pipes in both engines (one pointing up and one is straight), doing my research on the internet, i ...
3
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2answers
156 views
How do turbofan internals handle the load from the thrust?
To my understanding, turbofan engines get the majority of their thrust from the fan in front of the engine, up to around 70-80% while the core flow generates around 20-30%.
Forward movement is ...
5
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3answers
260 views
Can Flex thrust be lower than climb thrust?
Let's restrict this question to airliners with 2 jet engines.
For the remaining of the question, I'll use the term flex to designate reduced take off thrust as I'm more familiar with airbus's systems....
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2answers
478 views
What is the GE90-115b turbine power output in horsepower?
The GE90-115b is rated at 513 kN maximum thrust and is often said to have 110,000 shaft horsepower, but I have yet to find any document or specification that backs the claim on horsepower figure.
A ...
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1answer
407 views
Are there any airliners capable of vertical climb with engine thrust only by pointing the nose up?
So, sort of inspired by this question, I was wondering if there were any passenger airliners with enough thrust to fly straight up, supported purely through the thrust of their engines rather than the ...
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1answer
162 views
What is the thrust balance between compressor and exhaust nozzle for a turbojet engine?
I had this question asked in university and the teacher was unable to provide more than a theoretical estimate. The ratio I was given was 15/85.
Obviously in the case of a turbofan this ratio ...
0
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2answers
119 views
What are the criteria for conceptual design of thrust reverser in the use of braking?
I'm doing a project: Study of aircraft braking and pre-sizing of associated subsystems. We tried to find criteria for the reverser in the braking phase. I read FAR 25, but I did not find it.
Is there ...
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3answers
3k views
How does the bypass air provide thrust?
To my knowledge, bypass air produces 80% of total thrust. But I don't understand to how it does that. By accelerating the air, by increasing the speed or increasing the pressure of the air? Is it ...
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1answer
424 views
Turboprop vs Turbofan: How to compare Specific Fuel Consumption
I understand that Turboprop engines have a lower Specific Fuel Consumption (SFC) than Turbofan engines, on average. I want to see this for myself by analysis, ideally by comparing values of SFC for ...
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1answer
96 views
Can someone please tell me all the units for the propeller thrust equations?
This answer is excellent:-
Is there any equation to bind velocity, thrust and power?
except that it is (in practice) unusable, since all the units are missing.
I'm guessing we use meters for length ...
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1answer
164 views
Which is better: a rotor / prop followed by a stator, or contra rotating rotors / props?
It is all in the title.
I'm interested in power absorbed/used for a given thrust, or thrust generated for a given power (same diameters of course).
Just thrust and power. Ignore materials, electric ...
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3answers
1k views
Why is thrust available constant with speed for turbojet engines, when it varies with speed for turboprop engines?
Similarly, why is power available (nearly) constant with speed for a propeller engine, while it varies for a jet engine?
2
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0answers
221 views
Can the assumed temperature be lower than the flat rated temperature?
I was playing with reduced takeoff thrust in a Boeing 737-800 simulator yesterday and was surprised that I could enter assumed temperatures below the flat rated temperature of the engines. The ...
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1answer
158 views
Why don't we see diverging nozzles or diffusers?
When it comes to fully subsonic propulsion, all outlets are converging nozzles (I did say fully subsonic so no converging diverging). From what I understand, they are flow regulating devices (changing ...
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2answers
4k views
Do multi-engine jets need all engines with equal age to reduce asymmetry in thrust and fuel consumption arising out of deterioration?
Let's assume, one of the engines on a twin-jet needs replacement and the jet is is fitted with an old engine and a newer engine after the due replacement, the older engine would tend to produce less ...
5
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2answers
209 views
Do surfaces ahead of propellers decrease thrust?
I have had this question for ages, nearly impossible to find anything on the web. My experiments confused me even further! Its concerning the blockage effects of surfaces ahead of a propeller. For ...
9
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2answers
698 views
Are thrust levers synchronized by default when pushed/pulled? [duplicate]
When I watched this video about the last flight of Juergen "J.R." Raps from SFO to FRA in an A380 (before his retirement) I noticed he lines up or synchronizes the four thrust levers as shown between ...
5
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1answer
670 views
Does a turboshaft's exhaust provide any thrust?
See the below figure. Does the exhaust gas coming out through the nozzle have any force?
If the exhaust gas has force then how is it controlled by the helicopter?
3
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1answer
336 views
Can a Bombardier CRJ derate the takeoff thrust?
I have recently been flying a Bombardier CRJ 700 in a simulator and wondered how to derate the engines for takeoff.
I know how the takeoff thrust derating is selected in Airbus and modern Boeing ...
2
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1answer
159 views
How to design a near vertical take off airplane?
How to design a near vertical take off airplane, conceptually?
Say I have an airplane, similar to a Zenith 701. Say that it has a stall speed of 50 mph and a wing area of 60 sq ft, and it weighs ...
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1answer
446 views
Why limit the bank angle to 10° when passing through FL300 on a B737-800?
When passing thought FL300, we are instructed to set the bank angle limiter on the MCP to 10°.
I know one of the reasons for this is that we are thrust limited so maneuver capability decreases.
Are ...
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1answer
123 views
Is there any equation on propeller thrust that takes into account the number of blades [duplicate]
I had a look at both
What is the equation for calculating static thrust?
and
Is there any equation to bind velocity, thrust and power?
However, it does not mention how much would the thrust be ...
