JAGflyer From Canada, joined Aug 2004, 3320 posts, RR: 4 Posted (8 years 3 weeks 2 days 14 hours ago) and read 4901 times:
From all the pics I have seen they only have or use the inboard thrust reversers (engine 2 and 3). Does the A380 only have them on those engines or did they just use the inboards in all those photos?
Supported the beer and soda can industry, recycle old airplanes!
ZBBbird From Canada, joined Jul 2004, 58 posts, RR: 1 Reply 1, posted (8 years 3 weeks 2 days 14 hours ago) and read 4878 times:
As far as I know they only have thrust reverse on the inboard engines. The reason being that with the A380's large wingspan their would be more danger of the outboard engines ingesting FOD as they would be at the edge or over the edge of the runway.
Sabenapilot From Belgium, joined Feb 2000, 2697 posts, RR: 49 Reply 2, posted (8 years 3 weeks 2 days 11 hours ago) and read 4771 times:
Just before you ask:
Reversers are not taken into account is the calculation of the stopping distance of a plane. On modern planes, the pilots simply select a deceleration rate of the plane upon landing and an automatic system does the rest. Should they decide to use some T/R, all that would do is to put less braking force on the brakes, but the plane would not stop on a shorter distance.
FDXMECH From United States of America, joined Mar 2000, 3251 posts, RR: 38 Reply 3, posted (8 years 3 weeks 2 days 10 hours ago) and read 4721 times:
Quoting Sabenapilot (Reply 2): Reversers are not taken into account is the calculation of the stopping distance of a plane.
Not because thrust reversers provide a negligable slowing force rather these calculations are based on only basic equipment -brakes. And not based on new brakes able to absorb lots of kinetic energy but worn down to the limits.
Quoting Sabenapilot (Reply 2): On modern planes, the pilots simply select a deceleration rate of the plane upon landing and an automatic system does the rest. Should they decide to use some T/R, all that would do is to put less braking force on the brakes, but the plane would not stop on a shorter distance.
The T/R's when using auto-brakes are an added component used to reach a desired deceleration rate. Not a good criteria to say T/R's don't affect stopping dx.
What about without auto-brakes, OFF?
What about on wet runways?
Though thrust reversers aren't used in determining stopping distance, the plane can't be dispatched with more than one inop.
If the A380 only has two T/R's, it was to address a weight problem.
MrChips From Canada, joined Mar 2005, 911 posts, RR: 0 Reply 5, posted (8 years 3 weeks 2 days 8 hours ago) and read 4665 times:
Not only that, but consider the noise issue. Many of the airports the A380 will operate out of, such as LHR, have severe noise restrictions and quotas, meaning that many operators choose to forego the use of reverse thrust anyways.
FDXMECH From United States of America, joined Mar 2000, 3251 posts, RR: 38 Reply 7, posted (8 years 3 weeks 2 days 4 hours ago) and read 4586 times:
Quoting MrChips (Reply 5): Not only that, but consider the noise issue. Many of the airports the A380 will operate out of, such as LHR, have severe noise restrictions and quotas, meaning that many operators choose to forego the use of reverse thrust anyways.
I sincerely doubt it. If noise is that large an issue at certain airports, then simply don't use reverse thrust.
I believe leaving off two T/R's is simply a weight savings issue. Anything else is a public relations ploy. Spin if you will.
I don't see or hear many foreign operators negate the use of reverse thrust here at EWR.
MrChips From Canada, joined Mar 2005, 911 posts, RR: 0 Reply 8, posted (8 years 3 weeks 2 days 2 hours ago) and read 4571 times:
How is what I said "spin"?
I was simply stating that many airports that the A380 may operate out of have severe noise restrictions...much more strict than any airport here in North America.
Therefore, if its not going to be used, or is restricted in use, why include it in the airplane?
I think what happened here is a "cause-effect" situation...I had a potential cause, and FDXMECH another congruent cause as well:
Cause - noise restrictions, ever-pressing need to save weight,
Effect - delete T/R from engines #1 and #4.
I can imagine that deleting the reversers goes a ways to reduce complexity as well.
Jamie757 From , joined Dec 1969, posts, RR: Reply 12, posted (8 years 3 weeks 15 hours ago) and read 4398 times:
Quoting Sabenapilot (Reply 2): Should they decide to use some T/R, all that would do is to put less braking force on the brakes, but the plane would not stop on a shorter distance
Surely thrust reversers would reduce the distance taken for a plane to stop?
Air2gxs From , joined Dec 1969, posts, RR: Reply 13, posted (8 years 3 weeks 15 hours ago) and read 4394 times:
Quoting Jamie757 (Reply 12): Surely thrust reversers would reduce the distance taken for a plane to stop?
If the auto-brake system is not used, the reversers will aid in slowing the aircraft and decrease stopping distance. If auto-brakes are used, the stopping distance will not change. The deceleration rate is set by the flight crew and maintained by the computer. Any added effect from the thrust reversers would be added to the equation and the braking action from the brakes would be reduced. Thus, stopping distance is un-affected by the reversers.
Jamie757 From , joined Dec 1969, posts, RR: Reply 14, posted (8 years 3 weeks 14 hours ago) and read 4392 times:
Quoting Air2gxs (Reply 13): If the auto-brake system is not used, the reversers will aid in slowing the aircraft and decrease stopping distance. If auto-brakes are used, the stopping distance will not change. The deceleration rate is set by the flight crew and maintained by the computer. Any added effect from the thrust reversers would be added to the equation and the braking action from the brakes would be reduced. Thus, stopping distance is un-affected by the reversers.
I understand now, thanks for the simpletons guide!! Lol
Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17 Reply 15, posted (8 years 3 weeks 13 hours ago) and read 4379 times:
There is an exception to this, where the autobrake has a MAX position. In that case the brakes will be applied fully, with no demanded deceleration rate. Thrust reverse in this case will reduce stopping distance.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 38 Reply 16, posted (8 years 3 weeks 13 hours ago) and read 4375 times:
This according to Airbus.com.
_________________________________________________________________ Environmental Friendliness
The A380 will help cope with growing passenger numbers without negatively impacting the environment, thanks to significantly reduced noise and emission levels. In spite of its higher weight and thrust requirements, the A380 will make less noise than its closest competitor, while carrying 30 to 50 per cent more people. Current noise certification rules (ICAO "chapter 3") will be met by significant margins and the A380 will be compliant with the strictest local noise regulations, classified QC2 for departure from London's busy airports and QC1 for arrival.
For ground operations, the A380 can taxi with only two engines if required, will use only two thrust reversers and will employ a low-noise auxiliary power unit to help eliminate any noise concern.
_________________________________________________________________
Starlionblue From Hong Kong, joined Feb 2004, 15870 posts, RR: 66 Reply 19, posted (7 years 6 months 2 days 20 hours ago) and read 3689 times:
Quoting Jamie757 (Reply 12): Surely thrust reversers would reduce the distance taken for a plane to stop?
If autobrakes are used maximally yes, but reversers can still not be used for the calculated stopping distance. That is, they are a bonus, but your calculations have to assume they don't exist.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
474218 From United States of America, joined Oct 2005, 6340 posts, RR: 10 Reply 20, posted (7 years 6 months 2 days 10 hours ago) and read 3658 times:
Quoting Jetlagged (Reply 15): There is an exception to this, where the autobrake has a MAX position. In that case the brakes will be applied fully, with no demanded deceleration rate. Thrust reverse in this case will reduce stopping distance.
What about anti-skid system it has to be taken into consideration?
Quoting ZBBbird (Reply 1): As far as I know they only have thrust reverse on the inboard engines.
So you must have at least two different spare engines, 1 inboard and 1 outboard, another added expense to an all ready expensive aircraft.
OldAeroGuy From United States of America, joined Dec 2004, 3206 posts, RR: 66 Reply 22, posted (7 years 6 months 1 day 18 hours ago) and read 3508 times:
Quoting Starlionblue (Reply 19): If autobrakes are used maximally yes, but reversers can still not be used for the calculated stopping distance. That is, they are a bonus, but your calculations have to assume they don't exist.
On icy runways, most pilots are happy to have all the reverse thrust they can get.
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
Starlionblue From Hong Kong, joined Feb 2004, 15870 posts, RR: 66 Reply 23, posted (7 years 6 months 1 day 16 hours ago) and read 3486 times:
Quoting OldAeroGuy (Reply 22): Quoting Starlionblue (Reply 19):
If autobrakes are used maximally yes, but reversers can still not be used for the calculated stopping distance. That is, they are a bonus, but your calculations have to assume they don't exist.
On icy runways, most pilots are happy to have all the reverse thrust they can get.
I get that, but you can't really "count" on them in your calculations. This doesn't mean they won't be used of course
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
Pihero From France, joined Jan 2005, 3495 posts, RR: 72 Reply 24, posted (7 years 6 months 1 day 11 hours ago) and read 3450 times:
We seem to forget the A-380 dimensions, here.
To put things into perspective, the centreline of the outer engines are some 52 meters apart. That means that with the engines' diameter slightly less than four meters, each outer engine hangs only two meters inside the width of a 60 m runway. As the 744 manual states that at take-off power, the suction volume extends more than 35 feet around the engine, the likelyhood of ingestion appears quite real (I safely assume that the 380 ingestion volume will be a lot greater on 380 engines.)
On the weight question :
FedexMech, I think we need to qualify your observation :With the outer engines hanging that far out on the wing, I would also think that the wing bending relief they bring could mean a lot of weight saving on 1/ the wing structure and 2/- on the wing-to-fuselage attachment. How much compared to a T/R installation, I don't know but with such dimensions, I would bet on a lot.
A totally unconfirmed rumour last year was about AI needing to harden the airplane's structure as the whole airframe was close to a 1hz resonnance frequency, which was prejudicial to the occupants comfort, hence the fattening up of the aircraft. I happen to believe that rumour.
On the necessity of T/Rs :
The debate is wide open. What I can say is that I've seen airplanes dispatched with inoperative reversers -yes, a twin-engined aircraft can be dispatched without T/Rs except on contaminated runway take-offs - and that in Europe, local noise limitations prevent their use outside an emergency.
Let's not also forget that the 380 braking efficiency is greater than a 744's, because 1/-the landing and take-off speeds are much lower and 2/-the braking energy is distributed on a greater number of brakes (20 iso 16).
Just my two cents.
Contrail designer
25 Boeing nut: There was another post on this sometime back and I was certain that the A380 had four reversers. In fact, I was very bullheaded about it. Until that i
26 TristarSteve: No, The thrust reversers are in the C (orD) ducts which are part of the airframe. When you change an engine you open the C ducts and lower the engine
27 Starlionblue: Just to clarify, the risk of ingestion on the outboards is of course there during takeoff as well, but any ingested turf or other junk would just be b
28 Jetlagged: I think that off runway FOD is much more of a problem to the A380 in the takeoff case than in the reverse thrust case, for the reason you give (the s
29 OldAeroGuy: No longer true and it never was true for UKCAA regulations. With the advent of FAR25 Amendt. 98, the FAA and EASA (formerly JAA) now allow the use of
30 474218: Thanks TristarSteve, I remember that now, all my engine experience (which is very limited) was on J-58's and RB-211's.
32 474218: No problem, Airbus has said they have triple computer backup on all systems?
33 Pihero: So has Boeing. Then what is your point ?
34 474218: Is it not Airbus philosophy that there is no problem that three computers can not get you out of, or better yet, not let you get into.
35 Jetlagged: Any number of computers won't stop an engine failing.
36 777236ER: Small point, but generally the MAX autobrake setting still commands a deceleration rate. The maximum braking strength can be achieved using full manu
37 Jetlagged: The someone was me. The point I was making was that while reverse thrust can certainly kick up FOD, potentially for ingestion, takeoff thrust will al
38 Starlionblue: As I said, if you have FOD during forward thrust, it'll probably just go out the back unless it's something large (planespotter holding camera). But
39 HAWK21M: Considering the Angle created by the Deflected Reverse thrust to that by the Suction at the Inlet.I don't think they can be compared.The Reverse Thru
40 Jetlagged: Good point, but unless it's something large it won't do much damage, in which case the engine will suffer too.
41 Jetlagged: Not on any Airbus, nor on the 747, at least.
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