Talk:Thrust reversal/Archive 1
Untitled
[edit]The text states "the illustration shows a Target Reverser, where all of the efflux is reversed." Is there a missing illustration? This made me wonder if the text might be a copyvio (i.e., copied from a source with the illustration in question) but nothing turned up in a Google search. -- Gyrofrog (talk) 06:41, 30 January 2006 (UTC)
Pacific Western Airlines 311 was a airliner that crashed in 1978 in Cranbrook, BC, Canada. It was a 737 that was making a landing early, so they had to abort due to the snowplow still being on the runway. When they took off, Reverser 1 jammed and caused a crash. I don't know if the flight number is 311, but I remember hearing about it. I'll reasearch it and come back later. It might be worth adding to the article.Delta Elite
rename proposal
[edit]Shouldn't this really be called Thrust reversal or thrust reversers, rather than reverse thrust. I once read a comment by a pilot who said "Reverse thrusters are what spaceships have, thrust reversers are what airplanes have".--Joe 1987 12:46, 13 May 2006 (UTC)
idle reverse thrust
[edit]The explanation of the reverser itself makes perfect sense, however I have no idea what it means for an engine to 'spool up'. As far as I could tell from the article, normal operation of the reverser simply involves the reverser being activated, I didn't read about any other changes to the engine. --Rb 12:50, 9 July 2006 (UTC)
Automatic deployment?
[edit]I'll have to see some sources for aircraft with automatically deployed thrust reversers... Automatic wheel brakes and automatic ground spoilers are fairly common, but I dont' think I've ever seen an aircraft with automatic thrust reversers.
- I agree, I have experience of the operation of many modern commercial airliners and have never come across 'automatic' reverse thrust deployment. Essentially this would be very dangerous as the flight crew may decide to execute a go-around after the aircraft has touched down for several reasons, and they are not permitted to do this if reverse thrust has already been deployed. As there is no source for this feature being installed on any aircraft I will remove this reference in a week or two unless anyone wishes to provide a source (don't think they will find one though!). 82.44.26.36 21:18, 26 June 2007 (UTC)
Done - I have amended the article accordingly to remove reference to automatic deployment.
- The Panavia Tornado has the facility for automatic thrust reversal, rocking the throttles outboard pre-arms the system, switches in the undercarriage sense touchdown and deploys the reverser 'buckets' and raises all four spoilers into a 'lift dump' position. A long time since I worked on them and I remember that it was not generally used. Just need to find a reliable source and mention can be made of it again. Nimbus (Cumulus nimbus floats by) 20:03, 27 May 2010 (UTC)
No reverse for 247or DC-2, and is reverse pitch the same as reverse thrust?
[edit]The "Multiengine" section lists the Boeing 247 and Douglas DC-2 as being the first planes to ahve reverse thrust. I don't believe this is true. Both planes had variable-pitch propellers, but I do not believe they had a reverse-pitch range. Can anyone confirm this?
Also, it's questionable whether a reverse-pitch propeller is the same thing as reverse thrust. Many people think of the prop as a giant fan, but as far as I know it's actually a rotating wing. Changing the pitch changes the blades' angle of attack and increases "lift" (which pulls the plane forward). Hence the prop works even when there's not a clear path behind it (ie the plane's fueselage). When a prop is reversed, is it not creating lift in the opposite direction, just as an elevator can create lift "up" or "down" to change the whole plane's AoA? And if that's the case, does it really count as reverse thrust? If I'm correct, it's not "blowing" the thrust forward as in a jet engine, its' creating lift that pulls backwards and slows the plane.
- Yes, propellers that have the capability of reversing to the point that they blow the air forward, instead of backward, are referred to as "reversible propellers." They had that on the DC-6, DC-7 and most other airliners of that era. It was SOP to use "reverse thrust" upon landing, to shorten the distance of the roll-out and reduce the wear on the brakes, the same as is done with jetliners. EditorASC (talk) 09:20, 26 March 2010 (UTC)
Effectiveness at low speed
[edit]Most sources quote that reverse thrust (turbo jet or fan) reduces in effectiveness proportionately with a reduction in airspeed.
As the airspeed is reduced, reverse thrust and rudder effectiveness diminish somewhat proportionately. Nose steering is usually unnecessary until a speed of about 50 knots is reached.[1]
Reverse thrust is most effective when used at high runway speeds, and less effective at low speeds, therefore early selection of reverse thrust is desirable. Use of reverse thrust at speeds below approximately 60-70 knots can cause engine damage through sand, stones and other foreign objects entering the intake having been initially lifted off the runway by the forward flowing air. Surging (compressor stall) is also a possibility as the hot exhaust air is re-ingested at the intake.
I can't yet find an explanation as to why this is, but I suspect it has to do with the aerodynamic effects of reverse thrust, along with the negation of positive thrust that all jet engines produce at idle.
Thrust-reverse related accidents
[edit]I removed the Air Florida accident from this list, because the use of reverse thrust at the gate, was NOT cited as a contributing factor, in the NTSB report. Airdisaster.com was simply wrong on that point.
I also adjusted the wording on the Concorde crash, because it implied there was a reverser FAILURE on the DC-10, which was not the case.
I also have rather strong reservations about the following three accidents, listed in that section:
- At least three accidents have been blamed in part on late deployment of reverse thrust:
* On 8 December 2005 Southwest Airlines Flight 1248 overran the runway at Chicago Midway Airport, killing a 6-year old boy in a car. It was confirmed in the official crash report that delayed reverse thrust played a role.
* On 2 August 2005 Air France Flight 358 overran the runway at Pearson International Airport, Toronto, Canada. The plane came to a skidding halt 200 metres past the end of the runway, with the nose pointing down a ravine. This crash was partly attributed to the late deployment of the thrust reversal systems. All passengers and crew were able to exit the plane and survive.
* On 17 July 2007 TAM Airlines Flight 3054, an Airbus A320, was not able to stop while landing at Congonhas International Airport in São Paulo, Brazil, killing all 187 people on board and 12 on the ground. One inoperative thrust reverser played a role in the crash.
The wording needs to be revised, or better yet, deleting all three accidents from this section. Simply because late reversing was not the cause of any of those accidents. The planes are certified to land and stop on given runways, without the use of reversing at all, if the planes were at a legal landing weight for the given runways, all weather and runway conditions considered. The accidents were caused by other factors, not by "late reversing." I will wait a few days, and if there are no reasonable objections, I will remove those three accidents, from this section. EditorASC (talk) 09:44, 26 March 2010 (UTC)
- Although thrust reversers are an MEL-able item, that doesn't mean that they can't help prevent an accident. Yes, all of the crashes you referenced involved other factors, and you are correct in stating that an a/c must be certified to land and stop at their destination airport based on current weather. The one possible exception is the result of changing destination conditions from predicted weather that occur while the a/c is in flight. In these cases the use of thrust reversers may be necessary to stop within a safe distance. 208.65.175.197 (talk) 17:10, 2 August 2010 (UTC)
Powerback
[edit]I'd like to see a section on powerback - the use of Thrust reversal at the gate instead of gate to push back the aircraft. This was common with many American airlines until 2005-6 Savlonn (talk) 12:42, 26 January 2013 (UTC)
Removal of target type mentioned as 'flower' thrust reverser.
[edit]Done a few major changes on this article including more references and further explanation and the 3 types are now classified and mentioned properly but this particular information was probably wrong and I could not find anything to back it up other than a slight mention of its name.
| Target type |
|---|
| In the target-type thrust reverser, the reverser blades angle outward, giving the general appearance of flower petals, and forcing engine thrust to flow forward. |
-Ugog Nizdast (talk) 13:28, 16 July 2013 (UTC)
This article is wrong.
[edit]The article is wrong. Reverse thrust does not work by changing the direction of the fluid flow. It works by applying a force to a plate.
When a fluid stream (air or water, for example) is applied to a flat plate, the stream applies a force to the plate. You can see this when you hold a bucket under a water faucet and turn on the water. You will feel the force applied to the bucket. If you attach a plate to an aircraft and apply a fluid stream to the plate, the fluid will apply the force to the plate and, hence, to the aircraft. If the fluid stream is directed to the rear, the force will be directed to the rear. And it will slow down the aircraft down.
If the reverse thrust gizmos (whatever type is used) turned the fluid flow toward the front, how can that slow down the aircraft? Just before the gizmo the fluid is flowing to the rear and providing forward thrust. If you turn the flow you will provide the same velocity, but just in a forward direction. The net effect would be zero and reverse thrust wouldn't work. The only way reverse thrust can work is by applying the fluid stream to a plate--the reverse gizmo--that is attached to the aircraft.
Of course, you can't confine the fluid flow; you must have a way for the stream to get away, so the gizmos allow the fluid to get away from the engine. When you hold the bucket under the faucet the bucket catches the water. But if you used a flat plate, the water would splash in all directions, and you'd feel the force. The reverser gizmos direct the flow so it doesn't just go everywhere.
It should be obvious that you don't get a tremendous amount of force from this system, but you get some--enough to make a difference. I think that the BAe-146 doesn't have reverse thrust, so it's not always necessary. The best way to have reverse thrust on a jet would be to turn the engine around. But I don't think that's practical.
The article is wrong. wa6bjh (talk) 15:54, 16 June 2017 (UTC)
- Do you also think that rockets can't fly in a vacuum because "there's nothing for them to push against"? Andy Dingley (talk) 14:15, 19 June 2017 (UTC)
Of course rockets can fly in a vacuum. I've read Robert Goddard's article. And he was correct. And I remember something about Isaac Newton, too. The rocket works because the fluid flows in one direction and the rocket goes in the other direction. If reverse thrusters worked the way the article describes, the fluid would flow in both directions at the same time. In one instant the fluid would be applying a forward thrust and in the next instant--when it turned around--it would be applying the same thrust in the reverse direction. How is that going to slow the plane down?
If you look at one of Robert Goddard's rockets in the Air and Space Museum or at the city museum in Roswell, New Mexico, you will see how he controlled the rockets. The rockets had small vanes that were pushed into the exhaust stream. I think the Germans stole the system for the V-2, also. Anyway, the exhaust stream applied a force to the plate and because the plate was attached to the rocket, the force applied a torque to the rocket and turned it. It was the force on the plate, not something that pushed the exhaust stream to one side. wa6bjh (talk) 23:23, 25 June 2017 (UTC)
- You have been mislead into continuing this argument based on personal understanding of physical mechanisms. The only important thing with regards to this article is whether the theses can be supported by high-quality sources. Whether the article is "right" or "wrong" is irrelevant. Find a reliable source to support your argument and it will be included in the article. Ariadacapo (talk) 06:21, 26 June 2017 (UTC)
Reciprocating engines and thrust reversal?
[edit]I was struck by the following statement.
Reciprocating engine, turboprop and jet aircraft can all be designed to include thrust reversal systems
The article did not address the issue of getting reverse thrust from piston engines. How can an engine that doesn't provide forward thrust provide reverse thrust? Running a turbocharger in reverse? I'd like to see this claim addressed.
- A controllable pitch prop (standard for anything more than light aircraft) that has enough movement to go into reverse pitch. It's not common these days, as there are few piston-engined aircraft large enough to need it, but it was in the '50s-'60s. Andy Dingley (talk) 00:04, 26 August 2017 (UTC)
Top picture is an A321 instead of an A320?
[edit]The layout of the windows - and indeed the registration of the aircraft identifies it as an A321. Maybe a little pedantic... — Preceding unsigned comment added by 2001:630:12:1028:A978:3653:81E9:3636 (talk) 17:34, 14 December 2017 (UTC)
First sentence in the article is wrong
[edit]Quote: Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust so that it is directed forward, rather than backward. /Quote
It should be: Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust so that it is directed backward, rather than forward. The airflow is directed forward when in reverse, however the thrust vector is of course pointing backward when in reverse. Otherwise the aircraft would accelerate, not decelerate. Rainer Hoffmann1957 (talk) 14:09, 9 July 2018 (UTC)