Originally Posted By: D189379
Originally Posted By: Bill in Utah
Then on landing they did not use the reverse on the engines. Asked why and the crew (pilots) had a "concern" with them so only used brakes and kept the noise up.
Bill
I didn't think the engines had reverse? I was under the impression they used full thrust after landing in case the pilot thought he wouldn't be able to stop before the end of the runway.
Sigh...
I don't know where to start on this thread. If you go to full power on landing, the airplane will take off again...so, uh, no, nobody but Navy Pilots landing on aircraft carriers go to full power on touchdown (the arresting cable will stop the jet with full power on it, otherwise, they have about 250 feet in which to get airborne again...).
Thrust reverse is typically used to aid in stopping from high speed on landing, but it becomes less effective at low speed and at low speed, the flow, and debris on the runway, can be ingested by the engine.
If it is quiet on landing, then thrust reverse was not used, or not used heavily...if it's noisy on landing, then the engines are in reverse and the RPM was increased. If the noise was "kept up" then reverse was used.
In the aviation trivia category: it turns out that carbon based brakes wear less when hot. So, large aircraft, like the 777 and newer 747s will use minimum reverse. That saves wear and tear on the engine, while heating up the brakes...and by heating them, they last longer.
An airplane can be flown without thrust reversers - if there is a problem, the mechanics can bolt them in place, but the take off weight, landing weight and runway must be considered. Interestingly, when an airplane is certified for rejected takeoff (an abort, in which it is stopped on the runway) it uses only brakes and spoilers for stopping, since a common reason for rejected takeoffs (which are rare) is an engine failure, in which no reverse thrust would be available from that engine.
The A-320 has lousy brakes, they're small and so impose brake energy limits on the airplane's performance (both landing and takeoff), so if you don't use reverse on landing, or stop quickly, they get hot, limiting how soon the airplane can take off again (they have to be cool for takeoff to absorb the energy if the the takeoff is rejected and the airplane is stopped on the runway). Many airlines ordered the A320 family with Airbus' optional brake cooling fans; electric fans that blow cooling air over the brakes while the jet is on the ground...
Because of the brake limitations (they're carbon, just like the 777), Airbus pilots use full reverse on every landing...so it's always noisy...
As far as reliability goes, the A-320 is more complex than many aircraft, its flight control system is all fly by wire, but that doesn't make it more or less reliable. Those computers make fault tracing more easy...
All of those airplanes that do not have dump systems, like the A-320 or 737, can be landed over weight. Over weight landings are a big deal from a performance perspective, you have to be able to stop a heavy airplane in the runway available, given the conditions: wind (airspeed vs. groundspeed), contamination (rain, snow, ice), slope, aircraft weight, temperature and altitude.
Airplanes will not fly without hydraulic systems to operate the control surfaces unless you're lucky enough to be on a flight with an aviation legend like Al Haynes, who performed a far more miraculous landing (Google his name and UAL 232) than the "miracle on the Hudson" of Chesly Sullenberger. "Sully" had operating hydraulics...
Why a pilot would stay in the air with hydraulic system problem is beyond me...unless it was to fly to a runway on which the overweight airplane could be stopped...
Airplanes are often dispatched (released for flight) with inoperative equipment, but there are operating limitations placed on them. APU inop is common, but, as mentioned, one engine has to be started with ground air and power, then the air and power from the running engine can be cross-bled to start the other. There are a few limitations on an airplane with an inop APU, and it's up to the captain to determine if they are acceptable...as an example, on the Boeing 757, it limits the number of available power sources (APU generator is one) so the visibility minimums for landing must be raised.
Less common, but done, is an inoperative air conditioning pack....the "pack" is a turbo compressor, heat exchanger and expansion turbine that runs off engine bleed air and cools and compresses that bleed air for the cabin. The A-320 has two, but can be dispatched with one. The load for pressurizing and cooling the cabin can be handled by one pack, up to about 29,000 feet, so the airplane is restricted in altitude, and burns more fuel in the flight...airlines will dispatch an airplane that way to operate a critical flight and/or get the airplane to a base where it can be repaired. Sometimes that single pack struggles to keep up, and you get fluctuations in flow, as Bill described.
As far as Jet Blue - well, they're a hub and spoke airline, just like Delta, United and American. They're not point to point like Southwest, so they have exactly the same operating model as the legacy carriers, just a different cabin product. They're new to the business and have had some spectacular cases of inconveniencing passengers during adverse weather, including 11 hour sits on the ramp in JFK during snow...that's the fault of their management and crisis response. It has little to do with the A-320 as a platform. Blizzards in Denver don't pin United's fleet of 156 A-320s down like snow pins down Jet Blue in JFK...it's not a platform thing, it's an operational management thing...
