Airbus 320 question

[Hermes]

I just saw part of the landing of the plane on the Hudson and it occurred to me: With the engines inoperable, how much power does the plane have in its battery backup (I guess) and how long can it maneuver. I would imagine the employment of flaps, aileron, rudder etc. are very power consumptive.

The Gimly glider in Manitoba deployed a wind turbine (generator) to generate some power.

I guess in the Airbus case, the time was short and backup power sufficient?

Since a number of pilots had responded to our previous discussion, I wonder if they could shine some light on that issue.

[Jerry_75_Guy]

Well, I'm really out of my depth here since all of my types in heavy aircraft are for Boeing products, and so have little experience with the Airbus line, but you're on the right track.

 

Many transport category aircraft have a RAT (Ram Air Turbine, which you alluded to), used to provide power for flight controls should both engines and their hydraulic systems become inoperative, and of course various configurations of standard and emergency batteries to power electrics.

 

I've heard the Airbus line referred to as 'electric airplanes' because of the lack of manual systems relative to Boeing, and I know that has been a source of trouble at times for crew members.

 

I know without the engine driven generators running, the Hudson river A-320 probably lost some systems, but likely not much that they'd miss in the brief time they had before hitting the water.....with the exception of flaps; flap systems almost always actuate more slowly on backup systems, be they electrically or hydraulicly driven.

 

I'm sure someone else probably has more info.

[Francois_Dumas]

http://en.wikipedia.org/wiki/US_Airways_Flight_1549

 

 

[Mister Tee]

Also, most airliners are equipped with turbine APU's as well (small jet things in the tail cone you rarely notice).

 

I believe it was the 340 that was the first "fly by wire" Airbus, with solid linkages to the elevator and rudder trim tabs only. I read that for its FAA certification, it had to be demonstrated that it could be landed using the trim tabs only for control.

[Dennis Andress]

It's a question of where can emergency power come from. The APU (a small(er) jet engine in the tail) of a 747 for example can be used to route bleed air to Air Turbine Motors (ATM) in each engine pylon which turn hydraulic pumps for each of the 4 hydraulic systems. The same APU can turn two 75 KW generators for electricity. There's a lot of ifs involved though. Can the APU do all of that at the same time? If an engine shelled did it damage its pylon too much to use the ATM?

[azkaisr]

My company makes the APU (think third Jet on the Airbus 320). Our APU had a lot to do with the pilot maintaining control.

 

Pretty worthy

 

Kaisr

[Jerry_75_Guy]

My company makes the APU (think third Jet on the Airbus 320). Our APU had a lot to do with the pilot maintaining control.

 

Tell me more...

 

I considered the apu, but unless it was already running, I'd think it would be questionable whether having it in the loop for the couple of minutes they had available would have mattered much, in fact (and this relates to what I'd said about passing control in another thread) I'd read that the primary reason the Capt. took the controls was that since when both main gens went down, it left only the standby pwr to the left seat instruments, and the right side dark, implying no apu running at the time.

[azkaisr]

APU Story that I can share

 

It was working

[Hermes]

Thank you all for replying.

 

Reading your replies answers the basic Q that there is some considerable backup power, but leaves more Q unanswered:

 

Does the back-up APU and RAT run all the time or does it start when main generators fail (auto or man)?

 

How responsive would the plane be with the back-up power, e.g. does the pilot have enough control left to fly reasonable banking maneuvers, or is it pretty well straight ahead and maintain optimum glide angle/speed? Judging by the map in Wikipedea (thank you Francois for the link) he banked left fairly sharp.

 

..and if he would have landed on the tarmack, would he have had power to let down the wheels, or can they be employed and locked by gravity?

 

What about braking power (much needed when you can't reverse thrust!?

 

 

No need to go much further with this thread, for you can probably fill a few books with info on safety features and flying characteristics when same are employed.

 

it brings to mind the WWII returning bombers with nothing but prayers left and yet somehow managing to get the birds onto the ground (safely).

 

 

Thanks all.

[Kitsap]

My company makes the APU (think third Jet on the Airbus 320). Our APU had a lot to do with the pilot maintaining control.

 

Pretty worthy

 

Kaisr

 

Tom, I'm more familiar with that other aircraft manufacturer that uses you companies products. Would the APU in question be of the 331 series? Damn good unit for both pneumatic and electrical if that's the case.

[Mister Tee]

Thank you all for replying.

 

Reading your replies answers the basic Q that there is some considerable backup power, but leaves more Q unanswered:

 

Does the back-up APU and RAT run all the time or does it start when main generators fail (auto or man)?

 

How responsive would the plane be with the back-up power, e.g. does the pilot have enough control left to fly reasonable banking maneuvers, or is it pretty well straight ahead and maintain optimum glide angle/speed? Judging by the map in Wikipedea (thank you Francois for the link) he banked left fairly sharp.

 

..and if he would have landed on the tarmack, would he have had power to let down the wheels, or can they be employed and locked by gravity?

 

What about braking power (much needed when you can't reverse thrust!?

 

 

No need to go much further with this thread, for you can probably fill a few books with info on safety features and flying characteristics when same are employed.

 

it brings to mind the WWII returning bombers with nothing but prayers left and yet somehow managing to get the birds onto the ground (safely).

 

 

Thanks all.

 

APU's normally run all the time. In fact, that's how the engines are able to be started without the aircraft being hooked up to a power source. They also provide a redundant backup power source for the electrical system, including the hydraulic pumps for the flight controls, landing gear and brakes. Obviously, with no operational engines, there will be no reverse thrust capability, so the landing roll would be a lot longer than normal in a power out landing.

 

Even in the absence of power or a complete hydraulic failure, it's still possible to manipulate the control surfaces on most commercial jet airliners, as there are still solid linkages from the pilot controls to the control surfaces. Could you bank and flare a 747 by hand with no hydraulics? Don't know. Regional class jetliners? Piece of cake.

[Jerry_75_Guy]

Does the back-up APU and RAT run all the time or does it start when main generators fail (auto or man)?

 

The RAT is auto deployed in the event of a dual engine out on the systems I'm familiar with, but they can be manually deployed; definately not on all the time; it looks like a little windmill (~3ft acrossed) that pops out of an access panel on the belly. The APU is another matter, as Mister Tee mentioned, it is used for pneumatics (airconditioning, hyd. pressurization) and elec. when there's no gate power, but at least where I've worked, under normal operational circumstances we only used them when gate pwr was out, and shut them down after engine start for purposes of fuel savings.

 

How responsive would the plane be with the back-up power...

 

The planes fly fine on the RAT. Flaps come down slow on alternate pwr, and gear comes down and locks just fine, but it retracts slowly or usually not at all on alt. pwr, again at least on the systems I know.

 

What about braking power (much needed when you can't reverse thrust!?

 

Landing dist. table numbers are usually not created with rev. thrust as a variable, just brakes, and residual pressure in the brake system usually allows for at least 1 to 3 applications of the brakes when all else fails, but after you use all that, it just keeps rolling like a big shopping cart. Lots of pics on the web of screwups on the ramp where procedure wasn't followed and a plane bumped into something it wasn't supposed to.

 

[upflying]

I'm just a SEL/rotorcraft pilot and have no ATP experience. I can say that all pilots including A320 drivers have training in dead stick approaches (in a simulator). I would surmise that the A320 is perfectly capable of landing with both engines out (as in a fuel starvation incident) or the airplane would not be certified.

In the case of the Hudson River, Sullenberger made the very wise choice of landing wheels up. This caused the jet to land like a float plane by skimming across the water and extending the deceleration over a long period of time. This lessened the G-forces and resulted in 100% survivors. All airplanes can make at least one water landing.

[flars]

"All airplanes can make at least one water landing" I like that. Succinct. To the point. Droll.

I kind of place this up there with a retired British Army officer drinking his Cognac and smoking his cigar in the Explorer's Club referring to WWI or WWII as '...the recent disagreeable affair on the continent'.