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S/V Laura Ellen
09-14-2016, 10:38 PM
I saw the movie Sully the other day.
A couple of times in the movie the pilots made mention that Sully had started the APU before it was called for in the emergency procedures.
What is the significance of starting the APU as it pertains to this incident?
Was the APU required to fly/Glide the plane in for a water landing?

Gerarddm
09-14-2016, 10:42 PM
The only Apu I know is the deli mart owner in The Simpsons.

Pray, what is an APU?

S/V Laura Ellen
09-14-2016, 10:46 PM
Having very limited aviation knowledge, I may have got the acronym wrong, but I thoght the were talking about the Auxilary Power Unit (generator?).

Gerarddm
09-14-2016, 10:58 PM
Ah, thanks. I have zero avionics knowledge.

Jim Bow
09-14-2016, 11:18 PM
In the book "Fly by Wire: The Geese, the Glide, the Miracle on the Hudson", the author described it as a small propeller driven generator that dropped down into the airflow to provide electricity. Sully was grasping at straws and flipped a switch to engage the APU, when asked why he did it he said he didn't know.

Paul Girouard
09-14-2016, 11:30 PM
Not being a commercial aviation guy , I'd guess his APU might work inflight to provide some limited power to run flight essential instruments ?

In a Prowler and most of my era tactical jets we'd deploy a emergency RAT (Ram Air Turbine) a small if you will wind generator , again this would provide some essential electrical power .

The new tactical jets have APU's , and I think they have a battery that provides spark or what ever to fire off the APU , which you have right Auxiliary Power Unit . Having never worked on a jet that has one I don't know how they work .

But a jet with a APU doesn't need shore or ships electrical power, nor a "Huffer" , which is a Mobil mini jet engine that we'd hook up to our jet via a 4" air line , the "Huffer's " air would spin the jets engine and shore or ship electrical power would provide the electricity to fire the igniters , or spark plugs to fire off the motor.

So a APU, in a commercial jets must be able to provide emergency electrical power , in HOPE to re-fire the engines, which in Sully's case had been "FOD"-ed / FOD ( Foreign Object Damage) , any thing that goes down a intake can be FOD , screws , nuts , bolts , people , ducks , geese , etc all can damage the fan blades of the turbine , and if they get torn up they can't compress the air to create the thrust of a jet engine.

Paul Girouard
09-14-2016, 11:39 PM
In the bHudson"Fly by Wire: The Geese, the Glide, the Miracle on the Hudson", the author described it as a small propeller driven generator that dropped down into the airflow to provide electricity. Sully was grasping at straws and flipped a switch to engage the APU, when asked why he did it he said he didn't know.


I'm not sure that's right, could be , but a APU in a Growler FA-18 would be used as SOP (Standrad Operating Procedure) to start the jet on deck ashore or at sea , it's designed to be able to start itself without any ground support equipment.

A EA-6B , A-6 , F-14 , F-4 , A-4 that era tactical jet REQUIRED external power for the ship or shore power island , AND air to spin the motor , again either from a power island , or a tractor with a "Huffer" , to blow air to spin the turbine engine to fire off the engine.

So a wise aircrew knew they needed to land at a airport that HAD ground support equipment or the right provisions built in to get their jet re-started if they stopped for fuel.


Maybe a APU doesn't provide "flight essential" power, if Sully "didn't know" why he wanted to deploy "a small propeller driven generator" , what I'd call a RAT (Ram Air Turbine) or being so low he was now flying a glider , that flight essential was "him sitting in the pilots seat" and electrical power , or any kind wasn't going to do him any good. He was to low to air start his engines , and his engines where $hit by this time anyway , and wouldn't have re-fired if he had 20000 K do attempt a air start , he had what 1200 k to work with , or less!

CK 17
09-14-2016, 11:41 PM
I saw the movie Sully the other day.
A couple of times in the movie the pilots made mention that Sully had started the APU before it was called for in the emergency procedures.
What is the significance of starting the APU as it pertains to this incident?
Was the APU required to fly/Glide the plane in for a water landing?

if both engines had failed, and the APU was not started, they would have been operating on a standby electrical generator via a ram air turbine (RAT), which deploys automatically with the loss of both engines. They would have lost all electrical buses except for 4, plus batteries. They would have been down to a partial instrument panel and had a more crippled aircraft.

by starting up the APU, they had a full electrical system with the exception of some galley items. This would give them three hydraulic systems and a full electrical system. It would have also given them bleed air if they somehow got to the inflight engine restart checklist.

The APU was not required, but having it made life a lot simpler. Prolly more flight computers working, more control, more flight envelope protections etc.

during simulator training, we always start it before the checklist calls for it.

BrianW
09-14-2016, 11:42 PM
Not sure why Capt Sully needed, or wanted, the APU on his Airbus 320, but of the 5 airframes I have worked on with APU's, they all provided AC electrical power, some provided bleed air, and some provided hydraulic power. None of them were designed to provide all three, but it's certainly possible some APU's can do that.

Those are all good things to have when the main engines quit, and without an APU, the only thing providing electrical power is the DC system (mainly the battery.) Everything he needed to glide in should have been powered by the DC Essential Bus (the battery) but some nice to have items might only operate when the AC Bus is powered.

I'm also interested into the timing issue about when to start the APU. I hope our resident experts can help.

BrianW
09-14-2016, 11:43 PM
Ah, and CK 17 wrote his excellent reply while I was writing mine. :)

Paul Girouard
09-14-2016, 11:56 PM
Ah, and CK 17 wrote his excellent reply while I was writing mine. :)



You both suck, you've never landed on a carrier deck at sea! LOL!

CK 17
09-15-2016, 12:01 AM
Not sure why Capt Sully needed, or wanted, the APU on his Airbus 320, but of the 5 airframes I have worked on with APU's, they all provided AC electrical power, some provided bleed air, and some provided hydraulic power. None of them were designed to provide all three, but it's certainly possible some APU's can do that.

Those are all good things to have when the main engines quit, and without an APU, the only thing providing electrical power is the DC system (mainly the battery.) Everything he needed to glide in should have been powered by the DC Essential Bus (the battery) but some nice to have items might only operate when the AC Bus is powered.

I'm also interested into the timing issue about when to start the APU. I hope our resident experts can help.

theres no down side to starting the APU too early. There is a limitation that you must be below 25k altitude to start on the emergency electrical system.

The Airbus APU doesn't have a hydraulic pump per se, however, it does power buses that power hydraulic systems. The Airbus has 3 hydraulic systems: green which is engine powered off #1, blue which is electrically powered and yellow which is both engine #2 and electriclly powered.

With the the apu running, blue and yellow would be available and green would be be pressurized through a ptu from the yellow.

Paul Girouard
09-15-2016, 12:06 AM
theres no down side to starting the APU too early. There is a limitation that you must be below 25k altitude to start on the emergency electrical system.

The Airbus APU doesn't have a hydraulic pump per se, however, it does power buses that power hydraulic systems. The Airbus has 3 hydraulic systems: green which is engine powered off #1, blue which is electrically powered and yellow which is both engine #2 and electriclly powered.

With the the apu running, blue and yellow would be available and green would be be pressurized through a ptu from the yellow.

What is the air start altitude , preferred , and the air start minimums ?

Knowing a pilot would go well below minimums if given time , depending on emergency, I'd guess a guy would attempt to restart 5K below what was considered minimum restart altitude !

BrianW
09-15-2016, 12:44 AM
You both suck, you've never landed on a carrier deck at sea! LOL!

Unless they started putting Holiday Inn Express hotels, Five Guys, and liquor stores on carriers, I'm thinking not landing on a carrier at sea is a plus.

;)

BrianW
09-15-2016, 12:46 AM
The Airbus has 3 hydraulic systems: green which is engine powered off #1, blue which is electrically powered and yellow which is both engine #2 and electriclly powered.

Hydraulics systems identified by color... that's a first for me. Thanks!

Tom Wilkinson
09-15-2016, 01:43 AM
Hydraulics systems identified by color... that's a first for me. Thanks!

That's and airbus thing, the rest of the info has been well covered by CK17. No downside to starting it early and it's one of the first things I'd have done had I lost both engines, it's a simple and quick thing to do. I haven't seen the movie. Hope they got the details right.

The Bigfella
09-15-2016, 02:30 AM
Unless they started putting Holiday Inn Express hotels, Five Guys, and liquor stores on carriers, I'm thinking not landing on a carrier at sea is a plus.

;)


A mate of mine landed on the Reagan a couple of years back (and took off again the next day). No Holiday Inn, but he was given the Admiral's cabin.

Re Sully... I'm not sure if I'm mixing up incidents, but wasn't one of his engines still spinning enough to provide power/hydraulics anyhow?

Reynard38
09-15-2016, 06:39 AM
On the Mad Dog (MD88/90) with just battery power you are limited as to your flap and leading edge slat extension. This would dramatically raise your landing, or in Sullys case, ditching speed. As for energy to be disapated goes up this the square of the speed this would not be good.
I'd have gone for the APU as well. It's one quick motion to start it, and no downside.
Just had my sim training the other night. As CK said, after an engine failure I just start it.

CK 17
09-15-2016, 08:23 AM
A mate of mine landed on the Reagan a couple of years back (and took off again the next day). No Holiday Inn, but he was given the Admiral's cabin.

Re Sully... I'm not sure if I'm mixing up incidents, but wasn't one of his engines still spinning enough to provide power/hydraulics anyhow?
I haven read the report, but any speed above idle would provide adequate electrical and hydraulics and air. In this case the APU would be running and would automatically connect to the side of the electrical system not running.

CK 17
09-15-2016, 08:29 AM
Here's an example of a Airbus duel engine failure checklist:

http://www.ensampler.com/archives/594

Rum_Pirate
09-15-2016, 08:39 AM
You both suck, you've never landed on a carrier deck at sea! LOL!



https://www.youtube.com/watch?v=v4HTXBTkcpg

Surely the approach is 'controlled' by a computer calculating the speed of both Carrier and Plane, also the timing go the Carrier's pitching to minimise the possibility of a crash, e.g. into the tern of the Carrier.

Ian McColgin
09-15-2016, 08:41 AM
So long as there's carrier landing thread drift, Dad always felt that to get them up to PanAm standards he had to retrain the Navy vets because they don't learn to land: they crash.

Norman Bernstein
09-15-2016, 08:42 AM
I have NO expertise in this area, although I am a fan of things that are aviation-related. Maybe some of you professionals can answer this:

I thought that the APU of an airliner was actually a small jet turbine engine, capable of being started on battery power; I have always presumed that the APU exists to provide power for the main engine(s) starting, if no ground power is available... or that typically, ground power is not used for normal engine starts, so the APU provides the necessary power.

That being said, I should think that starting an APU takes time... enough time to ignite and spool up to the point where it IS providing power... is this not the case? If the Airbus was at just a few thousand feet of altitude, and was barely a minute or two from ditching, would the APU have been providing power quickly enough to be meaningful?

Reynard38
09-15-2016, 08:50 AM
Norman, good question and your knowledge of the APU is correct.
On the 88/90 the APU takes about a minute to start. I believe Sully had a little less than 4 minutes from bird strike to water landing.
Having the APU for me in this instance would have meant having normal flaps and slats. As I just had to do a no flap, no slat landing in the sim the other night I can recall the numbers.

No flap/no slat landing speed 194 knots
Flaps 28/full slat landing speed at the same weight 142 knots.

Which would you rather hit the water at?

Reynard38
09-15-2016, 08:59 AM
https://www.youtube.com/watch?v=v4HTXBTkcpg

Surely the approach is 'controlled' by a computer calculating the speed of both Carrier and Plane, also the timing go the Carrier's pitching to minimise the possibility of a crash, e.g. into the tern of the Carrier.

Never had the pleasure of a carrier landing, but I've done one to a simulated flight deck painted on the runway at Dobbins ARB in a T-34. The pilot refers to an optical landing system referred to as a "meatball". Hence the phrase "call the ball" when he sees it.
A carrier landing is a hand flown stick and rudder excercise. And a damned impressive one at that!

Norman Bernstein
09-15-2016, 09:02 AM
Norman, good question and your knowledge of the APU is correct.
On the 88/90 the APU takes about a minute to start. I believe Sully had a little less than 4 minutes from bird strike to water landing.
Having the APU for me in this instance would have meant having normal flaps and slats. As I just had to do a no flap, no slat landing in the sim the other night I can recall the numbers.


Are the systems in the Airbus equivalent? Assuming the loss of both engines, does it mean that the plane has lost flaps/slats completely without the APU running?

Another question: if the APU is used for engine start, when is it typically turned off? As soon as the main engines are fully functional? Why don't they leave the APU on until gear-up?

amish rob
09-15-2016, 09:11 AM
Every part of carrier operations blows my mind.

Peace,
Robert

Paul Girouard
09-15-2016, 09:15 AM
Never had the pleasure of a carrier landing, but I've done one to a simulated flight deck painted on the runway at Dobbins ARB in a T-34. The pilot refers to an optical landing system referred to as a "meatball". Hence the phrase "call the ball" when he sees it.
A carrier landing is a hand flown stick and rudder excercise. And a damned impressive one at that!

"Call the ball" , comes from the LSO, he'll call the modex number on the approaching aircraft . So the A/C in the photo is Modex 203 , so " Aircraft 203, call the ball".
The reply from the cockpit , when the pilot see's the "ball" is "Roger Ball", if he can't find it , for what ever reason "Claire" is the call, add power and go around to try again.

Most of today tactical jets have a approach guidance system, but unless things have changed, even IF the A/C HAS it the pilots don't use it. So it's the pilot working the throttles , stick and rudder , a long with the LSO (Paddles) talking to him / her to add power , you're low , you're high, stick with it, etc as the A/C approaches the ship.

Reynard38
09-15-2016, 09:16 AM
Are the systems in the Airbus equivalent? Assuming the loss of both engines, does it mean that the plane has lost flaps/slats completely without the APU running?

Another question: if the APU is used for engine start, when is it typically turned off? As soon as the main engines are fully functional? Why don't they leave the APU on until gear-up?

CK will have to answer the Airbus questions.

As to when do we shut it down, yes typically once both engines are running. Exceptions are in hot weather we keep it up until just before takeoff for additional cooling and also in very low visibility take offs and landings for an additional source of backup power.

Paul Girouard
09-15-2016, 09:18 AM
So long as there's carrier landing thread drift, Dad always felt that to get them up to PanAm standards he had to retrain the Navy vets because they don't learn to land: they crash.

In your dad's day that had some truth in it. Low angle of attack , higher approach speeds , killed a LOT of naval Aviator back in the day.

After the Korean War they way the approach the ship changed to what is used today, high AOA, lower approach speeds , and the ability to "go around" if required.

The age of "Wooden ships and Iron men" if you will.

Norman Bernstein
09-15-2016, 09:30 AM
As to when do we shut it down, yes typically once both engines are running. Exceptions are in hot weather we keep it up until just before takeoff for additional cooling and also in very low visibility take offs and landings for an additional source of backup power.

As I admitted, I have zero knowledge or experience in this stuff.

It just seems a bit strange. When flying in my friend's Piper (Arrow or Cherokee, I don't remember, it's a low wing with retractable gear), he turns on the electric fuel pressure boost pump and leaves it on until he's got altitude... and turns it back on before landing. Seems to me that it's a conservative measure to insure some level of redundancy.

If the Airbus loses flaps and/or slats in the event of the loss of both engines, and there isn't enough battery power to operate the hydraulics, it would seem prudent to have the APU on, in ANY situation where the plane is close to the ground and the loss of both engines would also mean losing control surfaces.

Am I misunderstanding this?

CK 17
09-15-2016, 09:47 AM
Are the systems in the Airbus equivalent? Assuming the loss of both engines, does it mean that the plane has lost flaps/slats completely without the APU running?

Another question: if the APU is used for engine start, when is it typically turned off? As soon as the main engines are fully functional? Why don't they leave the APU on until gear-up?
Part of the Airbus after start procedure is to shut down the apu. Occasionally, for performance reasons it is left running until after takeoff. In this case, with the apu running and the apu bleed on, the engine bleeds would remain closed and more engine performance would be available.

CK 17
09-15-2016, 09:50 AM
As I admitted, I have zero knowledge or experience in this stuff.

It just seems a bit strange. When flying in my friend's Piper (Arrow or Cherokee, I don't remember, it's a low wing with retractable gear), he turns on the electric fuel pressure boost pump and leaves it on until he's got altitude... and turns it back on before landing. Seems to me that it's a conservative measure to insure some level of redundancy.

If the Airbus loses flaps and/or slats in the event of the loss of both engines, and there isn't enough battery power to operate the hydraulics, it would seem prudent to have the APU on, in ANY situation where the plane is close to the ground and the loss of both engines would also mean losing control surfaces.

Am I misunderstanding this?

In in this case the RAT would automatically deploy providing hydraulic and AC/DC power to critical systems and instruments.

the APU would provide nearly a full electrical system. Essentially you are correct. However, occurrences such as this are so rare and even in this case the apu running or not didn't change anything.

Reynard38
09-15-2016, 09:56 AM
As I admitted, I have zero knowledge or experience in this stuff.

It just seems a bit strange. When flying in my friend's Piper (Arrow or Cherokee, I don't remember, it's a low wing with retractable gear), he turns on the electric fuel pressure boost pump and leaves it on until he's got altitude... and turns it back on before landing. Seems to me that it's a conservative measure to insure some level of redundancy.

If the Airbus loses flaps and/or slats in the event of the loss of both engines, and there isn't enough battery power to operate the hydraulics, it would seem prudent to have the APU on, in ANY situation where the plane is close to the ground and the loss of both engines would also mean losing control surfaces.

Am I misunderstanding this?

No you are not. However keep in mind the redundancies we've got on a typical airliner, and the rarity of what happened to Sully.
We can lose an engine with all the wheels still on the runway at maximum takeoff weight and if we are beyond a certain speed (referred to as V1) we continue the takeoff. We've actually have 4 separate hydraulic pumps on the jet, 3 generators and 7 fuel pumps.
The APU consumes 400 pounds of fuel per hour. Add in the hourly maintenance costs and you can see why our procedures call for running it only in certain circumstances after takeoff and in the air.

If if you were to lose both engines so low to the ground that there wasn't time to fire up the APU you'd most likely already be configured for landing, or if departing you'd at least have takeoff flaps and slats out which would lower your touchdown speed considerably.

Norman Bernstein
09-15-2016, 10:03 AM
If if you were to lose both engines so low to the ground that there wasn't time to fire up the APU you'd most likely already be configured for landing, or if departing you'd at least have takeoff flaps and slats out which would lower your touchdown speed considerably.

OK, I understand... thanks for the explanation.

I haven't seen the film, and I do understand that it's portrayal accuracy has been questioned... and the NTSB guys are apparently pissed at the portrayal of them as being 'hostile' (from what I've read in the media, at least).

Regardless, it seems to me the height of folly to criticize Sullenberger for his judgment in those four minutes. Whether there were, or were not, alternatives to landing in the Hudson, are strictly 'second guessing', and the guy acted heroically, IMHO.

Dave Hadfield
09-15-2016, 10:22 AM
Just to be clear, it takes :02 sec to start the APU (you just rotate a knob), then after it starts (about :30 sec) it gives you nearly full electrics, hydraulics, and on an Airbus with no generators working, it vastly improves the flight control computers.

There is no downside. It's a no-brainer.

The Bigfella
09-15-2016, 12:50 PM
https://photos.smugmug.com/Other/Pictures2/n-MbxPq/i-fBZzspj/0/M/i-fBZzspj-M.jpg

Bob Adams
09-15-2016, 02:21 PM
Amongst all the hype did anybody remember the guy in the right seat?

S/V Laura Ellen
09-15-2016, 02:31 PM
Thanks to those aviation types that have answered my questions.

The movie painted the NTSB members as jerks that were withholding information to make it appear that Sully could have safely landed to at least two airports. The NTSB members withheld that the pilots using the simulators practiced the landing 17 times before the final attempt that showed it could be done and that they were briefed on the proper approaches back to the airport prior to the attempts.

CK 17
09-15-2016, 03:23 PM
The ntsb are the ultimate Monday morning quarterbacks. Their smart, they are great advocates. However, they're investigators and don't necessarily understand line operations from a pilots perspective.

BrianW
09-15-2016, 04:17 PM
The APU consumes 400 pounds of fuel per hour. Add in the hourly maintenance costs and you can see why our procedures call for running it only in certain circumstances after takeoff and in the air.

I was going to bring this up. APU's cost money and time to operate, so they are normally turned off as soon as not needed.

Even on helicopters, it's usually turned off before take off.

Old Dryfoot
09-15-2016, 06:12 PM
Best thread this week.

Bob Adams
09-15-2016, 06:18 PM
Best thread this week.

Much better than the political mudslinging now dominating The Bilge

The Bigfella
09-15-2016, 06:25 PM
Best thread this week.


Much better than the political mudslinging now dominating The Bilge

Just wait until we get onto this Sully ditching, in New Guinea

http://air-war.org/Marlee2_in_water.jpg

Rich Jones
09-15-2016, 06:45 PM
Thanks to those aviation types that have answered my questions.

The movie painted the NTSB members as jerks that were withholding information to make it appear that Sully could have safely landed to at least two airports. The NTSB members withheld that the pilots using the simulators practiced the landing 17 times before the final attempt that showed it could be done and that they were briefed on the proper approaches back to the airport prior to the attempts.
I just saw the movie today and agree with what is said here. The NTSB are painted as guys out on a witch hunt. I believe the movie also takes "artistic liberties" with compacting the investigation. Those investigations don't move that fast.

CK 17
09-15-2016, 08:01 PM
Are the systems in the Airbus equivalent? Assuming the loss of both engines, does it mean that the plane has lost flaps/slats completely without the APU
Oops, sorry I think I missed this question.

A double engine failure does not mean the loss of flaps and slats in an A320. However, they would move at half speed I think, until the APU was up and running. . .

Paul Girouard
09-15-2016, 08:28 PM
What is the air start altitude , preferred , and the air start minimums ?

Knowing a pilot would go well below minimums if given time , depending on emergency, I'd guess a guy would attempt to restart 5K below what was considered minimum restart altitude !


Seeing you're doing reviews of missed questions what about mine about air re-start altitude?

CK 17
09-15-2016, 09:14 PM
Seeing you're doing reviews of missed questions what about mine about air re-start altitude?
According to my manual, the "windmill quick start" envelope starts at 220 kias as low as sea level provided N2 is at least 18 percent. For a "stabilized windmill relight" the chart says 260 kias are needed. There doesn't seem to be a preferred altitude. The envelope goes from SL to FL 300. The minimum speed for a starter assisted relight is 135 kias up to FL 150.

If there is an air source(APU or another engine), and the aircraft is outside the engine relight envelope, the start valve will automatically open.

so no reason to spend valuable time looking up a chart and yet another reason to start the APU ASAP.

hope this helps.

Paul Girouard
09-15-2016, 09:52 PM
OK, I think I see. Of course my navy training has me thinking differently . Our crews , because they can eject look at airspeed if they are low , so under 115 KAS or so they'd eject.

And IIRC as they get under 5K they would be looking at punching out soon !

But if you're at sea level at 220 KIAS you are in deep do do!!

The Bigfella
09-20-2016, 05:55 AM
Just saw Sully tonight (funnily enough, while my two girls are/were flying... one on a domestic flight in China, the other has about 90 minutes to go before landing in LAX... and on to Arizona).

Great movie.