Why Don’t Planes Use Reverse Thrust To Push Back?

When a plane departs an airport and pushes back from the gate, it uses a small but powerful ‘tug’ truck to reverse. But why don’t airlines save on the cost and use powerful jet engines to push back?

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#Aviation #Flight #Avgeek

[gpaull]

You missed the main reason. Today’s high bypass engines have a minimum speed that the reversers can by deployed at. If deployed below that speed, the engine exhaust can be sucked into the engine inlet causing compressor stalls. Compressor stalls can cause engine damage. I had to do a boroscope (internal engine inspection) on a 737 that used its reversers below the minimum allowable speed to prevent it from going off of the end of an icy runway.

[MSRTA_Productions]

"We have a 747 pushing back with reverse thrust. That has been out of protocol since the 1980s sir. You can ALT+F4" - Airforceproud95

[JetBOY]

A year ago our flight delayed because tug went missing in airport for that our captain passenger announced "our plane can fly but can't reverse" 😂

[dndd]

A few years ago, Airbus demonstrated a plane with electric motors in the landing gear. It looked like a good solution for pushback and taxi.

[JAldrich]

I was on a Delta 777 at Sydney Airport that performed a reverse thrust pushback from the gate. It was due to heavy rain, and they got permission from the tower to perform it. The captain informed us over the intercom they were about to perform the action. They originally told us they were going to use 2 engines, but then told us later they were only going to use 1 engine. The reason they told us that was so we weren’t scared when we saw only one engine working. The captain informed us that he guaranteed we would not go to Los Angeles without both engines working!

[dewiz]

I heard a DC9 pilot inform ATC that one of his engines had gone into reverse thrust while they were on approach. I heard it on the Flying Club radio while awaiting my flight lesson in Ottawa, Ontario in late 1996 or early 1997.

[ivonplay]

In the 90’s, I used to fly in an out of Atlanta on business a lot. The Delta pilots would use reverse thrust on their planes to back out of the gates. It was really kind of cool.

[robertoskeetrech]

Yes. About 20 yrs ago on a flight out of Boston. Reverse thrust was used to back away from the terminal. However, it was an Embraer Banderante - turboprop, not a jet. I experienced the same several times across the USA.

[markodom]

My memory goes back to the mid '60s. Planes then parked parallel to the concourse and either used outdoor push up steps or dual long jetways that loaded/unloaded the larger planes (707s & DC-8s) from the front and back. It was much faster with two exits instead of one on planes that carried 150 passengers instead of 300. When they started they simply continued forward turning 90 degrees left or right and so didn't need a tug or reversers.

In the 70's and 80's when airport universally went to straight in parking at a single, shorter, front jetway, backing up became necessary so tugs were used. Some were simply the typical tractors used for baggage carts but became larger special machines as planes got bigger. During that time I do recall seeing and being on planes that pushed back with the thrust reversers. It was loud and I recall at the time thinking it added a lot of wear and tear on the reversers that might present a maintenance problem. I noticed over the years airlines stopped doing that, apparently for the reasons in this story and as I noticed. I do recall also it was usually done only on the rear engined planes (DC-9s/MD-80s and 727s).

Interesting recollection - thanks

[spacurve]

Years ago I was in a A318 or A319 landing in a short, wet and windy runway in Guatemala City, was unique experience when the pilot activate the reverse thrust just before the wheels touching the ground, the sound ultra loud, vibration and fuselage stress was breathtaking, near to fail... near to waste the all runway, hahahahaha the people when feeled safe, claped and cheers the pilots.

[tulekit]

I've only been on a plane once that used jet powerback for departure, back in the 90s. The flight attendant forewarned passengers. I was (as usual) sitting in the back near the engines. It was probably a DC9. It was really REALLY loud. I loved it. I was fascinated. The louder the better. I'd love to see it done more, but it makes sense why it's not done.

[flitetym]

Noise and FOD ingestion. In fact, before there were outright prohibitions on “power-back”, there were curfews. Also, ATC clearance was required.

[harshjani]

I can hear AFP95 saying ‘thats been out of protocol, you are cleared to ALT F4’

[alsmith]

Interesting, but I'm afraid you're not quite right on this one. These are all valid reasons, but they are all secondary to that of the engines themselves. Having spent 15 years on development of civil aerospace engines, I know that the primary reason is actually down to re-ingestion of air into the engine itself. Even on landing, reverse thrust is supposed to be cancelled and the reversers stowed prior to dropping below a certain speed threshold, this is mandated for everything except emergency situations. Above this speed, the forward motion of the nacelle through the air keeps the air from the reverser clear of the intake, however, below this speed, the re-directed air can get ingested back into the intake. This air (having been through the Fan once already) is already warmer (and therefore less dense) than the ambient atmosphere and is also very turbulent. As this air passes back through the fan it can result in Fan flutter or even stall... both of which can be damaging to the blades!! Back in the 70's and 80's there were a couple of instances of fan blade failures, which were attributed to damaged caused by powered push backs. As such, this restriction has been in place for all aircraft, and all engine and airframe manufacturers put a lot of development time into determining this minimum safe reverser speed.

[ronaldoakes]

Circa 1999 (if I recall correctly), American Airlines regularly used reverse thrust to back their MD80s out of what is now known as Terminal B at DFW. I both experienced this as a passenger and witnessed this while waiting as I was flying AA frequently between ORD and DFW in that era.

[bER]

Back in 2004, I boarded an American Airiines MD80 at DFW and most of the Maddogs used reverse thrust to push back. It was wild, but until I realized what was actually happening, the noise inside the terminal concourse was very noticeable. It literally sounded like a plane was getting too close to the building!

[whatevermightwork]

In the 1980s and 1990s, I flew out of Burbank Airport in California (BUR, now Bob Hope Airport) on 727 and MD-8x aircraft that backed away from the gate area with reverse thrust. In the aircraft you heard engine noise elevate but not to the level of takeoff thrust.

Burbank was always fun as a passenger. They still don't have bridges so you walk out onto the ramp then up stairs. The terminal windows are at ground level so you'd get a great view of other jets backing out and debris flying towards the building, but I never heard of a window being damaged.

[gweebs]

back in the 70's Eastern Airlines in Atlanta used power pushback. one other negative: the terminal needs to be designed for FOD that is being thrown back at it: aka minimum windows or strenghtened windows that can take a blast of FOD, great vid!

[donkensler]

Reverse thrust to back away from the terminal was SOP for Northwest DC-9s until they were retired in (I think) the early-mid 00s. It was kinda cool - the pilot would go forward a couple of feet, then throw it into reverse to back up. Pilots would come on the PA to inform the passengers of the procedure and advise it was going to be pretty noisy in the last few rows of coach.

[billyboy]

I saw something recently where they use a small electric motor in the nose wheel to push back the aircraft.