3arrows From Slovakia, joined Nov 2008, 5 posts, RR: 0 Posted (4 years 6 months 6 days 13 hours ago) and read 1905 times:
Hi guys! I make one bachelor project about ground power augmentation (GPA). For more closely explain, it is same ground device, which can help aircraft with take-off from runway. So GPA generate kind of energy, which is afford to aircraft in time of take-off from runway. For realization this devices (GPA) can by ramp, electromagnetic forces (electromagnetic rail), or catapult. Advantages of GPA could by reduction of consumption fuel, annoying sound around airport and reduction of emission. So what You think about GPA? Can by GPA realized in operation? Thank you for your opinions.
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 1, posted (4 years 6 months 6 days 11 hours ago) and read 1874 times:
Considering the weight of todays commercial aircraft,the advantages would never be present.
Practically it would never work out.also what would be reliability & back up of the system correctly functioning.
Personally I can only think of small aircraft or UAVs.
This has been brought up before, and its a common misconception that some sort of ground catapult will save fuel. Before any sort of launch the engines will have to be at takeoff thrust anyway, you're not saving fuel just because the engines aren't technically launching the aircraft.
The only reason I can see for a GPA is where runway space is very limited (as an aircraft carrier).
If the runway is shorter then that could make it easier to get around noise restrictions, but it won't mean that the engines are at less thrust, thus producing less noise.
This has been brought up before, and its a common misconception that some sort of ground catapult will save fuel. Before any sort of launch the engines will have to be at takeoff thrust anyway, you're not saving fuel just because the engines aren't technically launching the aircraft.
The only reason I can see for a GPA is where runway space is very limited (as an aircraft carrier).
If the runway is shorter then that could make it easier to get around noise restrictions, but it won't mean that the engines are at less thrust, thus producing less noise.
Agreed. Not to mention that the aircraft would have to be made immensely heavier to withstand the stresses involved, which would more than offset any potential savings. You also are unlikely to find many passengers willing or eager to endure the G-loads that would ensue.
3arrows From Slovakia, joined Nov 2008, 5 posts, RR: 0 Reply 4, posted (4 years 6 months 4 days 10 hours ago) and read 1681 times:
what about passengers a G force. So the name of title it isn´t so good, becouse this device shouldn´t speed up the aircraft just as on aircraft carrier, but this device should by only compensation of the part of energy, wich is necessery to take-off from runway. It means, the passenger can feel the same G-force, wich is on normal take-off (in civil aircraft)
SB From United Kingdom, joined Aug 2006, 216 posts, RR: 0 Reply 5, posted (4 years 6 months 4 days 9 hours ago) and read 1671 times:
So essentially you nudge the aircraft into the air allowing a take-off with, for example, climb power set rather than take-off power? An interesting idea but I don't see it saving much fuel - the engines will still be running - and we already routinely use derated power (sometimes very close to climb thrust itself) for take-off to prolong engine life.
WPIAeroGuy From United States of America, joined Aug 2007, 240 posts, RR: 0 Reply 6, posted (4 years 6 months 4 days 9 hours ago) and read 1665 times:
Quoting SB (Reply 5): So essentially you nudge the aircraft into the air allowing a take-off with, for example, climb power set rather than take-off power? An interesting idea but I don't see it saving much fuel - the engines will still be running - and we already routinely use derated power (sometimes very close to climb thrust itself) for take-off to prolong engine life.
S.
If you're going to be at climb thrust at liftoff, wouldn't you also have to be at climb speed? In that case you'd have to increase runway length, which would most likely negate any benefits whatsoever.
Catapults and other systems have their purpose, its just not to save fuel. Maybe future engines will have reliability high enough so that there could be a powered launch under minimum thrust until a certain altitude at which point the thrust would increase, but I don't see it as being likely.
SB From United Kingdom, joined Aug 2006, 216 posts, RR: 0 Reply 7, posted (4 years 6 months 4 days 7 hours ago) and read 1635 times:
No, thrust required is a function of weight, acceleration and vertical gradient. The airspeed (V2) is also a function of weight, but isn't related to the thrust available. The take-off run would indeed be much longer due to reduced thrust, but that's where the nudge could come in.
Generally thrust reduction altitude is lower than acceleration altitude.
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From Slovakia, joined Nov 2008, 5 posts, 
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