kimberlyRJ
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Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 9:50 pm

Hello all,

I’ve noticed when working on the Boeing 747-400 aircraft our pilots often select engines 2 and 3 for reverse thrust leaving 1 and 4 at idle. Sometimes they will use all 4, but never only 1 and 4.

Is there an operational reason for this? Or just wear and tear?

I have also noticed that the inner slats ‘fold’ away when reverse thrust is selected, is this to stop lift or to stop the slats being damaged?

Many thanks

Kimberly.
 
pjflysfast
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 10:12 pm

Do you mean while they are are taxiing out? If so they may do that in order not to use the brakes because they can get hot real fast if you use them on taxi and that makes them less affective if you need to abort a takeoff. Also if they get less wear and tear on the breaks by doing that.
 
777wt
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 10:15 pm

Engine 1 & 4 is closer to the edges of the runway and FOD is a concern.
I think they never use 1 and 4 due to the inboard engines thrust reverse must be used due closer to the airframe and should a problem arise with reverse thrust, there won't be much loss of yaw control.

The inner slats fold when reverse thrust is selected to protect them from FOD and the airflow from the reverse thrust damaging the slats by pushing on them trying to get past the fully extended stops. This is also due to eng 2 & 3 closer to the ground.

[Edited 2008-03-20 15:16:56]
 
2H4
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 10:17 pm



Quoting Kimberlyrj (Thread starter):
Sometimes they will use all 4, but never only 1 and 4.

Is there an operational reason for this? Or just wear and tear?

1 and 4 are closest to the edges of the runway/taxiway, and thus, closest to debris that could be sucked into the engines. I'm not sure how heavily this susceptibility to foreign object damage weighs into the preference for using the inboards over the outboards, but I suspect it's a factor.

2H4
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askr
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 10:18 pm

Quoting Kimberlyrj (Thread starter):

I’ve noticed when working on the Boeing 747-400 aircraft our pilots often select engines 2 and 3 for reverse thrust leaving 1 and 4 at idle. Sometimes they will use all 4, but never only 1 and 4.

Is there an operational reason for this? Or just wear and tear?

If you mean during landing - it is to avoid creating a dust and debris cloud and having the engines ingest all of that.

That is one of the reasons why Airbus opted for no thrust reversers on tha a380. The 2 inner engines got them only because the regulators (mainly the FAA, not sure about Europe).

[Edited 2008-03-20 15:20:28]
ATC-PL Wanabe :) - 2nd application is in... 11 July...
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 10:59 pm

Thanks for your help guys

It makes sense what you were saying about the outer engines (1 and 4) not being selected for reverse thrust after landing.

Noticed that when landing at LHR the pilots normally use all four engines in reverse, but on the other hand at foreign airports such as Africa and South America we tend to use reverse on 2 and 3 only…

Once again, thanks for your help  Smile

Kimberly.
 
David L
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 11:19 pm



Quoting PJFlysFast (Reply 1):
Do you mean while they are are taxiing out? If so they may do that in order not to use the brakes because they can get hot real fast if you use them on taxi

Reverse during taxi on a 747? "I'm no expert but..." I'd be surprised.  Smile
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 20, 2008 11:51 pm

Hello

I have never seen a Boeing 747-400 use reverse thrust during taxi, however when exiting the runway at high speed the pilots sometimes seem to leave the engines in idle reverse, not sure why!?

Having worked for both Virgin Atlantic and now British Airways I have always noticed the GE engines sound very different during flight, but on landing in reverse the RR engines really growl, it’s a fantastic sound! Love it. Not sure about PW on the Boeing 744?

Kimberly
 
2H4
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 12:01 am



Quoting http://www.airliners.net/discussions/profile.main?username=Kimberlyrj:
My husband is a pilot (Capt), he started out at Finnair (MD11) then Virgin (B744)

Not to dissuade you from participating here in the forums, but don't you have an extremely accurate source of B747 information at your immediate disposal?  Wink

2H4
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kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 12:04 am



Quoting 2H4 (Reply 8):
Not to dissuade you from participating here in the forums, but don't you have an extremely accurate source of B747 information at your immediate disposal?

My husband is away on a two week trip so he is not here to ask  Sad Also he tends to be somewhat snappy when I start asking techy questions - I am female after all lol

Kimberly.
 
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jetmech
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 2:01 am



Quoting Kimberlyrj (Reply 7):
RR engines really growl

The RR actually stands for Raucous Rumble, the sound of pure, unadulterated power  Smile.

Quoting Kimberlyrj (Reply 9):
Also he tends to be somewhat snappy when I start asking techy questions - I am female after all lol

That's not nice  Sad . Do you get snappy in return when he starts asking questions about passenger comfort and cabin service standards? Most pilots I speak to can ramble on incessantly about flying, they love it! As the joke goes;

"Why do pilots always talk about flying when they are with women, and about women when they are flying?

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
Mir
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 2:32 am



Quoting 2H4 (Reply 3):
I'm not sure how heavily this susceptibility to foreign object damage weighs into the preference for using the inboards over the outboards, but I suspect it's a factor.

It's enough of a factor that Airbus decided not to fit reversers to the 380 on engines 1 and 4.

Quoting Kimberlyrj (Reply 5):
Noticed that when landing at LHR the pilots normally use all four engines in reverse, but on the other hand at foreign airports such as Africa and South America we tend to use reverse on 2 and 3 only…

At LHR, you most likely have someone coming in close behind you and ATC needs you off that runway yesterday. That's probably not the case at most other airports.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 5:30 pm

Hello All

Quoting JetMech (Reply 10):
The RR actually stands for Raucous Rumble, the sound of pure, unadulterated power

Don't I know it, love sitting by left 2 (the exit just infront of the wings) hearing the RR's power up then the pilots 'flooring it', odd thing is the RR engines make quite a nice sound as they power back from TOGA to CLB (climb thrust), oh and on landing I love them they really rev up, the rumble - oh yes, sounds better then my Bmw M3 when I floor it  Smile

Quoting JetMech (Reply 10):
That's not nice . Do you get snappy in return when he starts asking questions about passenger comfort and cabin service standards? Most pilots I speak to can ramble on incessantly about flying, they love it! As the joke goes;

"Why do pilots always talk about flying when they are with women, and about women when they are flying?

I think I ask to many questions - but you are right when ever I am in the flight deck the pilots are always asking advice or questions about either me, or another female lol Bless em

Quoting Mir (Reply 11):
At LHR, you most likely have someone coming in close behind you and ATC needs you off that runway yesterday. That's probably not the case at most other airports.

I bet that’s the reason, you can always see a long line of aircraft on finals.

I know that on early morning arrivals pilots are encouraged to not use reverse thrust to keep the noise down – but sometimes due to weather conditions they have no choice, safety always comes first (well, maybe second after chatting about females  Wink )

Kimberly.
 
2H4
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 5:40 pm



Quoting Mir (Reply 11):
It's enough of a factor that Airbus decided not to fit reversers to the 380 on engines 1 and 4.

Is the FOD risk indeed the primary reason for this?

Quoting Kimberlyrj (Reply 12):
I think I ask to many questions - but you are right when ever I am in the flight deck the pilots are always asking advice or questions about either me, or another female lol Bless em

So it sounds like both parties possess information the other wants. My advice - hold out on the female/relationship advice until they earn it by answering some of your aviation questions.  Wink

2H4
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kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 5:56 pm

Hey

Quoting 2H4 (Reply 13):
So it sounds like both parties possess information the other wants. My advice - hold out on the female/relationship advice until they earn it by answering some of your aviation questions

Good point, I shall stop bribing them with tea/coffee and First (class) food and hold out on the information front lol – Will also do up my second button on my uniform  Wink

Kimberly
 
2H4
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 6:08 pm

Quoting Kimberlyrj (Reply 14):
Will also do up my second button on my uniform

Woah woah woah....impose sanctions first, then escalate to DEFCON 1.

These things have to happen in stages, after all.  Wink

2H4

[Edited 2008-03-21 11:20:11]
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kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 8:10 pm

Hey

Quoting 2H4 (Reply 15):
then escalate to DEFCON 1

DEFCON 1 is undoing the third button when dealing with a male passenger who is complaining - or convinceing the commander he really does need to keep the seat belt sign on for say two hours  Wink

I think I need to fly with UA or NW to see what the PW engines sound like on take off, from what I have heard on the ground they don't sound so aggressive?

Kimberly
 
2H4
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 8:34 pm



Quoting Kimberlyrj (Reply 16):
DEFCON 1 is undoing the third button when dealing with a male passenger who is complaining - or convinceing the commander he really does need to keep the seat belt sign on for say two hours

Do keep us abreast of your progress with the information exchange.  biggrin 

2H4
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jetmech
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 8:41 pm



Quoting Kimberlyrj (Reply 14):
Will also do up my second button on my uniform

Woah woah woah, steady on there. There's withholding information, and then there's taking things wwwaaaaaayyy too far  Sad !

Quoting 2H4 (Reply 15):
These things have to happen in stages, after all.

Precisely. The sudden withdrawal of "eye candy" has dangerous side effects for any male  faint  .

Quoting Kimberlyrj (Reply 12):
I think I ask to many questions

I think us pilots and engineers on Tech / Ops should concoct a list of grindingly technical questions for you to ask your husband, or any other pilot for that matter. It would be priceless to see the deflated ego look in their eyes when the flight attendant knows more about planes then they do Big grin !

Quoting Kimberlyrj (Reply 16):
DEFCON 1 is undoing the third button when dealing with a male passenger who is complaining

LOL Ha ha. I'm not sure if this would calm a male passenger down, or further "gee"" him up!

Regards. JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
2H4
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 8:50 pm



Quoting JetMech (Reply 18):
I think us pilots and engineers on Tech / Ops should concoct a list of grindingly technical questions for you to ask your husband, or any other pilot for that matter. It would be priceless to see the deflated ego look in their eyes when the flight attendant knows more about planes then they do

I think JetMech is on to something here.

It's time for Tech-Oppers familiar with the B772 to volunteer their most tricky trivia questions. We need to arm Kimberly with some serious mental ammo so she can school her snappy husband.

So let's hear it, folks....what are the trickiest B772 questions from a systems and/or operational standpoint? What are some real kickers from your oral exams and checkrides?

2H4
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Starlionblue
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RE: Boeing 747-400 Reverse Thrust?

Fri Mar 21, 2008 10:51 pm



Quoting Kimberlyrj (Reply 12):
I think I ask to many questions

No you don't.

Quoting 2H4 (Reply 13):
My advice - hold out on the female/relationship advice until they earn it by answering some of your aviation questions.

Indeed. If your husband chooses to be annoying you, as a woman, are well armed to retaliate. From personal experience I would say that he doesn't know what he's messing with.  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Mir
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RE: Boeing 747-400 Reverse Thrust?

Sat Mar 22, 2008 2:43 am



Quoting 2H4 (Reply 13):
Is the FOD risk indeed the primary reason for this?

I'd think so. It could also be for weight savings (and it does save weight), but I doubt that the regulatory authorities would let that excuse fly. FOD risk would be a better excuse to leave them off.

Quoting 2H4 (Reply 19):
So let's hear it, folks....what are the trickiest B772 questions from a systems and/or operational standpoint? What are some real kickers from your oral exams and checkrides?

This website should prove useful: http://www.smartcockpit.com/plane/boeing/B777/  Smile

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
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Francoflier
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RE: Boeing 747-400 Reverse Thrust?

Sat Mar 22, 2008 2:31 pm



Quoting Mir (Reply 21):
but I doubt that the regulatory authorities would let that excuse fly. FOD risk would be a better excuse to leave them off.

Interesting... Do certifying authorities require the presence of TRs?

Quoting Kimberlyrj (Reply 16):
DEFCON 1 is undoing the third button when dealing with a male passenger who is complaining - or convinceing the commander he really does need to keep the seat belt sign on for say two hours

D@mn... I need to make a few suggestions to the ISD department at our airline.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Sat Mar 22, 2008 10:59 pm

Hey all

Firstly thanks for all your help, it's great chatting to you guys - really enjoying it  Smile

Quoting JetMech (Reply 18):
Woah woah woah, steady on there. There's withholding information, and then there's taking things wwwaaaaaayyy too far

Your right, doing up the second button would only mean the pilots play up, or keep on asking if everything is ok - oh, when I say pilots I also include some female pilots who bat for the other side  Wink

Quoting JetMech (Reply 18):
Precisely. The sudden withdrawal of "eye candy" has dangerous side effects for any male

I don't want to send the commander into shock, your right. Maybe I will ask him to use loads of thrust on take off and lots of reverse on landing and I will go to DEFCON 1 (the thrid button) - If things start getting really stressy then there is the fourth button but that’s reserved for code one red situations only (well, normally unless its my husband who is the commander lol)

Quoting JetMech (Reply 18):
LOL Ha ha. I'm not sure if this would calm a male passenger down, or further "gee"" him up!

It normally takes their mind of what they are complaining about. If that fails you try the friend approach, take em off to a cabin crew jump seat, sit nice and close and pretend you really care, while coming across as sweet and innocent as possible – how else did you think I made it to Cabin Service Director and Compliance Manager by 28.

Quoting 2H4 (Reply 19):
It's time for Tech-Oppers familiar with the B772 to volunteer their most tricky trivia questions. We need to arm Kimberly with some serious mental ammo so she can school her snappy husband

I think that’s a great idea, give me some questions, I will catch him out. He does not like it when I tell him stuff about the cabin that he does not know…

Quoting Francoflier (Reply 22):
D@mn... I need to make a few suggestions to the ISD department at our airline

Lol, you should off the record we have found that the BUA (button/s undone approach) really does help  Smile

Once again guys, thanks so much for your help, I think I'm going to enjoy posting here  Wink

Kimberly.
 
Mir
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 2:01 am



Quoting Francoflier (Reply 22):
Interesting... Do certifying authorities require the presence of TRs?

From what I've heard, the FAA was the driving force behind including TRs on the 380. Airbus had planned on leaving them off.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
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jetmech
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 7:29 am



Quoting Kimberlyrj (Reply 23):
Your right, doing up the second button would only mean the pilots play up

A male in the throes of going cold turkey from "eye candy" with-drawl is a pathetic sight indeed!

Quoting Kimberlyrj (Reply 23):
(well, normally unless its my husband who is the commander lol)

This is the precise time to ask technical questions! Your husband would not want to lose face in front of the FO, and the presence of the FO will reduce the likelihood of any "snappiness". I dread to think of what will happen if he does not know the answer however  Wow! !

Quoting Kimberlyrj (Reply 23):
sit nice and close and pretend you really care, while coming across as sweet and innocent as possible

LOL, Hahaha  Smile. I have no doubt that works, it would on me, but I'm not usually one to complain. Do you accompany the above with "puppy dog eyes" or "doe like, deer lost in the forest eyes"? I really like those myself  cloudnine 

Quoting 2H4 (Reply 19):



Quoting Starlionblue (Reply 20):



Quoting Kimberlyrj (Reply 23):
I think that's a great idea, give me some questions, I will catch him out. He does not like it when I tell him stuff about the cabin that he does not know...

Ask him which centre hydraulic system demand pump operates when both of them are selected to the "ON" position (answer is the C1 pump). Then ask him why both cannot run simultaneously (no answer provided by Smart Cockpit, but I presume it is because there is not enough bleed air to run both at the same time). Check page 8 and 9 of the following link;

http://www.smartcockpit.com/pdf/plane/boeing/B777/systems/0007/

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
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Francoflier
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 7:56 am



Quoting Mir (Reply 24):
From what I've heard, the FAA was the driving force behind including TRs on the 380. Airbus had planned on leaving them off.

Well, I can see why they would twitch a bit... It's a big heavy bird.
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
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Starlionblue
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 9:29 am



Quoting Francoflier (Reply 26):
Quoting Mir (Reply 24):
From what I've heard, the FAA was the driving force behind including TRs on the 380. Airbus had planned on leaving them off.

Well, I can see why they would twitch a bit... It's a big heavy bird.

Let's not start that again. At least not in this thread.  Wink
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 1:30 pm



Quoting JetMech (Reply 25):
This is the precise time to ask technical questions! Your husband would not want to lose face in front of the FO, and the presence of the FO will reduce the likelihood of any "snappiness". I dread to think of what will happen if he does not know the answer however

I think him and I have an understanding on the flight deck, I don’t challenge him (to much) and he keeps his hand off my bottom (and certain other areas) – well, on the flight deck anyway.

Quoting JetMech (Reply 25):
LOL, Hahaha . I have no doubt that works, it would on me, but I'm not usually one to complain. Do you accompany the above with "puppy dog eyes" or "doe like, deer lost in the forest eyes"? I really like those myself

As long as it remains with in certain limitations eyes, shift and a shortening of the dress can always help… Yes with have ‘puppy dog’ eyes are in use most of the time with passengers. When it comes to the female passengers we wheel out our male flight attendant, we do have quite a few now that are not gay (while most of the gay crew can charm anyone!)

Quoting Mir (Reply 24):
From what I've heard, the FAA was the driving force behind including TRs on the 380. Airbus had planned on leaving them off.

I am not sure if I understand, Rolls Royce and Airbus were planning on not having reverse thrust fitted on the engines? Is that not a little crazy?

Kimberly.
 
2H4
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 2:50 pm



Quoting JetMech (Reply 25):
"doe like, deer lost in the forest eyes"? I really like those myself

What are you doing.....drugging them before the date?  eyebrow 

Personally, I don't find incoherence all that attractive...  Wink

Quoting Kimberlyrj (Reply 28):
I am not sure if I understand, Rolls Royce and Airbus were planning on not having reverse thrust fitted on the engines? Is that not a little crazy?

Not all transport-category jet aircraft have reversers. The Do-328, Avro RJ series, and certain Fokker models come to mind.

2H4
Intentionally Left Blank
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 4:02 pm

Hey

Quoting 2H4 (Reply 29):
Not all transport-category jet aircraft have reversers. The Do-328, Avro RJ series, and certain Fokker models come to mind

I was once told by an Avro 100 pilot that due to the positioning of the landing gear on the fuselage they can apply a lot more breaking power then if they were fitted to the wings – not sure if this is true though…

Also they have speed breaks on their backside which are used on finals no? I mean on the BAe 146 and Avro etc…

I just thought it would be better to be safe then sorry and lets face it, British Airways are getting the A380 RR version and they need to sound as sexy as on the B744 or I will be complaining to Willie himself! lol

Kimberly.
 
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Jetlagged
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 5:33 pm



Quoting Kimberlyrj (Reply 30):
I was once told by an Avro 100 pilot that due to the positioning of the landing gear on the fuselage they can apply a lot more breaking power then if they were fitted to the wings – not sure if this is true though…

Sounds like a bit of a pilot's line shoot. No reverse thrust is mainly to save weight, and as you say the Avro/BAe146 (and the F.28) have large tail speedbrakes as well as liftdumpers so stop very well without reverse. The Avro/146 also has a ground idle thrust setting which helps reduce stopping distance too.

The fuselage mounted gear does help with operations from rough fields though, which was part of the original design concept.

Quoting Kimberlyrj (Reply 23):
Once again guys, thanks so much for your help, I think I'm going to enjoy posting here

I think we're all going to enjoy you posting here too.  Smile You had my undivided attention as soon as you started talking about undoing buttons. And to think I thought BUA meant British United Airways.  blush  Your profile reads like a aviation nerds wet dream: a woman who likes aviation, flight sims AND football.....  melting 
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 23, 2008 7:21 pm

Hello

Quoting Jetlagged (Reply 31):
I think we're all going to enjoy you posting here too. You had my undivided attention as soon as you started talking about undoing buttons. And to think I thought BUA meant British United Airways. Your profile reads like a aviation nerds wet dream: a woman who likes aviation, flight sims AND football.....

Coming from a family of four bothers and me being the ‘baby’ I had no choice about enjoying football (soccer) and also learning how to deal with men/boys.

As for aviation my Mother is the only one who broke the family code, she is the Chief Surgeon at a major trauma hospital. Dad is an Air Chief Marshal in the RAF. One of my brother’s fly in the Navy and the three others fly with airlines as pilots, two with British Airways and one with Virgin Atlantic.

So football and aviation is in my blood and I love it, along with cars (more modern cars then older ones) and flight sim, I really enjoy it – trying to keep it real as much as possible…

Hope we you all had a great weekend? I’m so enjoying the long weekend, going up in my husbands Cessna tomorrow (weather permitting, fingers crossed).

Enjoy your long weekend  Smile

Kimberly.
 
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jetmech
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RE: Boeing 747-400 Reverse Thrust?

Mon Mar 24, 2008 3:39 am



Quoting 2H4 (Reply 29):
What are you doing.....drugging them before the date?

Nah, I just think big beautiful eyes with a touch of innocence are a very attractive feature on a lady.

Quoting Kimberlyrj (Reply 28):
I am not sure if I understand, Rolls Royce and Airbus were planning on not having reverse thrust fitted on the engines? Is that not a little crazy?

I think it was actually an Airbus initiative as part of their weight reduction programme for the A380. Airbus was confident that braking technology had progressed to the point that thrust reversers were not needed. Most of the retardation effort comes from the brakes. It seems that the FAA thought it was a crazy proposition, thus the A380 has reversers on the inboard engines.

Quoting Kimberlyrj (Reply 30):
I was once told by an Avro 100 pilot that due to the positioning of the landing gear on the fuselage they can apply a lot more breaking power then if they were fitted to the wings -- not sure if this is true though...

Possibly. With a high wing aircraft, having the landing gear under the wings (instead of the fuselage) means that you would have a far greater torque moment to absorb at the landing gear mountings for a given braking force between the wheel and tarmac. This is due to a wing mounted landing gear being taller than a fuselage mounted one.

Quoting Kimberlyrj (Reply 32):
As for aviation my Mother is the only one who broke the family code, she is the Chief Surgeon at a major trauma hospital. Dad is an Air Chief Marshal in the RAF. One of my brother's fly in the Navy and the three others fly with airlines as pilots, two with British Airways and one with Virgin Atlantic.

Wow, what a distinguished family!

Quoting Jetlagged (Reply 31):
I think we're all going to enjoy you posting here too.

Agreed. Great to have you here Kimberley  Smile !

Regards, JetMech
JetMech split the back of his pants. He can feel the wind in his hair :shock: .
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Mon Mar 24, 2008 11:35 am



Quoting JetMech (Reply 33):
Possibly. With a high wing aircraft, having the landing gear under the wings (instead of the fuselage) means that you would have a far greater torque moment to absorb at the landing gear mountings for a given braking force between the wheel and tarmac. This is due to a wing mounted landing gear being taller than a fuselage mounted one

I was once on a PalmAir FlightLine BAe 146-300 taking off from BOH (Bournemouth International Airport, Dorset, England - where I live) and just over half way down the runway with engines screaming away and the commander decided to abort the take off. I have never felt anything like it, the BAe 146 just ‘stopped dead’ so hard in fact passengers where first throw into the seats in front of them, and then slammed back into their seats with great force, much more then I had never seen on any Airbus’s or Boeing’s. Thought it was weather conditions, we had at least 2500ft of runway left at stopping, winds calm and dry runway – the stopping ability was amazing.

PROBLEM is, no reverse thrust and as I love the sound, the Bae/Avro remands towards the bottom of my top five aircraft!

Quoting JetMech (Reply 33):
It seems that the FAA thought it was a crazy proposition, thus the A380 has reversers on the inboard engines.

Record this moment guys and don't tell my husband BUT I think the FAA were making sense in this case, it’s always a good idea to have a back up system and when I have seen the Airbus A380 landing (which has been 8 times so far) they have always been using reverse thrust, so it must be a hit with pilots.  Wink

Have a great Easter Monday guy's - enjoy those Egg's  Smile

Kimberly
 
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Starlionblue
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RE: Boeing 747-400 Reverse Thrust?

Mon Mar 24, 2008 12:20 pm



Quoting Kimberlyrj (Reply 34):
Record this moment guys and don't tell my husband BUT I think the FAA were making sense in this case, it’s always a good idea to have a back up system and when I have seen the Airbus A380 landing (which has been 8 times so far) they have always been using reverse thrust, so it must be a hit with pilots.

It's not much of a backup system since it doesn't even have close to the same stopping power. You'd think a triple (or is it quadruple) redundant brake system and eight braked axles with sixteen braked wheels would be enough.

If you don't have the brakes you're going off the end whether you have reversers or not.


Also, were they using actual reverse or just idle reverse?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Mon Mar 24, 2008 5:13 pm



Quoting Starlionblue (Reply 35):
It's not much of a backup system since it doesn't even have close to the same stopping power. You'd think a triple (or is it quadruple) redundant brake system and eight braked axles with sixteen braked wheels would be enough

Sorry I did not mean back up as a failure, I meant as a back up in normal operations. As pilots always say you can never have enough assistance when taking off or landing.

IV always been told that in certain weather conditions and reverse breaking can be (at high speed) as effective as wheel breaking? Also on the Boeing 747 having four engines able to reverse, if there were issues keeping the aircraft on the runway the pilots could not only use differential breaking (gear) but also one (or two or three engines) in reverse to help turn the aircraft suddenly or effectively.

When I was on the flight deck on a flight landing at MIA during a really heavy rain storm and high cross winds and the pilots engaged reverse on engine 3 and then about four seconds after engine 2 then about five seconds after that engines 1 and 4 at the same time, each seems to have an effect on ‘steering’ the Boeing 744 and put the nose straight on the centre line.

Quoting Starlionblue (Reply 35):
Also, were they using actual reverse or just idle reverse?

If your talking about the amazing stopping BAe/Avro at BOH, the aircraft’s engines (AlliedSignal) are not fitted with reverse thrust, so the engines would have been at idle.

If your talking about the aborting on the Airbus A320, Airbus A321, B722, B733, B734, Boeing B744, B772, B752, B763, L1011 & DC10 (all the aircraft I have worked on, and at some point had aborted full stop take off’s) all aircraft seemed to use a lot of reverse thrust if not maximum.

As I am sure you know aborting a take off is often more dangerous then just getting the bird into the sky. My husband (Capt) confirmed that on the B772 on take off, if they totally have no choice and abort take off, they do one of two things in concern of reverse thrust

1. Reduce engines to idle and wait a six seconds then select reverse slowly increasing the amount of reverse to how much is needed, maximum is maximum…

2. If there is a need to stop the aircraft ASAP then engines to idle and reverse thrust to maximum straight away.

Of course I am only covering the use of reverse thrust in what I’m talking about not RTO settings, speed breaks etc

I'm flying out on BA117 (LHR to JFK) on Tuesday morning, anyone else on her? if so give me a shout  Wink

Kimberly
 
Mir
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RE: Boeing 747-400 Reverse Thrust?

Tue Mar 25, 2008 12:38 am

Reverse or no, the aircraft must be able to stop on the runway (in whatever condition it's in) without the use of reverse thrust. So there's no real need for it in terms of landing performance, and it does reduce weight if you don't fit them.

-Mir
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tdscanuck
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RE: Boeing 747-400 Reverse Thrust?

Tue Mar 25, 2008 3:50 am



Quoting Kimberlyrj (Reply 36):
IV always been told that in certain weather conditions and reverse breaking can be (at high speed) as effective as wheel breaking?

That's true, but it's not because the reversers get better, it's because certain conditions cause braking to get worse (ice, lots of water, etc.). If you find that out when you hit the runway, you're going to go off the end whether you've got reversers or not.

Quoting Kimberlyrj (Reply 36):
Also on the Boeing 747 having four engines able to reverse, if there were issues keeping the aircraft on the runway the pilots could not only use differential breaking (gear) but also one (or two or three engines) in reverse to help turn the aircraft suddenly or effectively.

The time to spool up and down on an engine that large is too long to be used for sudden changes. The staged example of introducing reverse thrust makes sense in a predictable situation, like a cross wind, but I don't see differential reverse thrust as a useful alternative to rudder and nose when sudden turns are called for.

Quoting Mir (Reply 37):
Reverse or no, the aircraft must be able to stop on the runway (in whatever condition it's in) without the use of reverse thrust.

That's not 100% true...there are situations (lousy weather, generally) where you can take some credit for reversers, since they delay the degradation of your stopping performance as the brakes start to lose effectiveness. You still need the brakes though.

Tom.
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Wed Mar 26, 2008 6:52 pm

Hello

Quoting Tdscanuck (Reply 38):
That's true, but it's not because the reversers get better, it's because certain conditions cause braking to get worse (ice, lots of water, etc.). If you find that out when you hit the runway, you're going to go off the end whether you've got reversers or not

What I meant is the slower the aircrafts speed, the less effective the reverse thrust from an aircraft.

As for going off the end of the runway, that hardly ever happens, thanks to planning etc. As my husband says there is always a number of bank up plans on landing, and going off the end of the runway is not normally one of them.

Quoting Tdscanuck (Reply 38):
The time to spool up and down on an engine that large is too long to be used for sudden changes. The staged example of introducing reverse thrust makes sense in a predictable situation, like a cross wind, but I don't see differential reverse thrust as a useful alternative to rudder and nose when sudden turns are called for

I love reading up on aircraft accidents and incidents. I have noticed that on quite a few incidents especially those were the aircraft got into issues on landing the pilots used differential reverse on the engines, a prime example of that was the American Airlines MD80 accident at Littlerock. The Captain applied different amounts of reverse two the two engines to assist the direction of the aircraft.

If the worst should happen on landing, while reverse does have a lag on responding (in selecting from idle) it can be extremely effective in steering the aircraft or helping to be kept on the runway.

I don’t think anyone is saying reverse could ever replace breaking, but, nor the other way around either.

A jet lagged Kimberly.
 
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Starlionblue
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 27, 2008 12:15 am



Quoting Kimberlyrj (Reply 39):
I don’t think anyone is saying reverse could ever replace breaking, but, nor the other way around either.

"the other way around" would be that braking replaces reverse? Yes it can, as evidenced by the large number of aircraft without reversers.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
tdscanuck
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 27, 2008 12:40 am



Quoting Kimberlyrj (Reply 39):
What I meant is the slower the aircrafts speed, the less effective the reverse thrust from an aircraft.

Why would that be? At low speeds, like landing, the amount of thrust the engine can produce isn't a function of airspeed.

Quoting Kimberlyrj (Reply 39):

I don’t think anyone is saying reverse could ever replace breaking, but, nor the other way around either.

Airbus actually tried to say exactly the latter (and I happen to agree with them) but the regulators didn't buy it.

Tom.
 
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Jetlagged
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 27, 2008 3:01 pm



Quoting Kimberlyrj (Reply 39):
What I meant is the slower the aircrafts speed, the less effective the reverse thrust from an aircraft.



Quoting Tdscanuck (Reply 41):
Why would that be? At low speeds, like landing, the amount of thrust the engine can produce isn't a function of airspeed.

It certainly is the case that with a big fan engine with no core reverser there is considerable net reverse thrust at 150 knots, but at 0 knots very little (that's one reason why "power back" is not much use with high bypass ratio engines). This is because a significant proportion of this net reverse thrust is in fact the intake momentum drag (ram drag) of the engine. As the aircraft slows down this reduces linearly with speed until when static you are left with the reverse thrust from the partially reversed fan airflow offset by the forward thrust from the core. When I say partially reversed, I mean that although all the air has been deflected it is not deflected through 180 degrees.

The opposite happens with net forward thrust as an aircraft accelerates: it decreases as ram drag increases (gross thrust being roughly the same).
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speedracer1407
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 27, 2008 6:28 pm



Quoting Kimberlyrj (Reply 39):
I love reading up on aircraft accidents and incidents. I have noticed that on quite a few incidents especially those were the aircraft got into issues on landing the pilots used differential reverse on the engines, a prime example of that was the American Airlines MD80 accident at Littlerock. The Captain applied different amounts of reverse two the two engines to assist the direction of the aircraft.

If the worst should happen on landing, while reverse does have a lag on responding (in selecting from idle) it can be extremely effective in steering the aircraft or helping to be kept on the runway.

Strange that you would use the Little Rock accident, in which the plane veered off the runway with fatal consequences, as evidence that differential reverse can be "extremely effective in steering the aircraft or helping to keep it on the runway."


Seems to me that the lesson here is the same others have been saying: if you get yourself into a situation where brakes and rudder are insufficient to stop and steer the aircraft, reverse thrust is not going to help much, if at all. Thus, it's not a last resort life-saver, nor any cheaper to buy, use, and maintain than wheel brakes in normal ops, nor even practical in most noise-restricted areas. For these reasons brakes can indeed "replace" RT all together with little or no safety implication.
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2H4
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 27, 2008 6:39 pm



Quoting Speedracer1407 (Reply 43):
if you get yourself into a situation where brakes and rudder are insufficient to stop and steer the aircraft, reverse thrust is not going to help much, if at all.

All it takes is one section of runway with poor to nil braking to see the value in having reverse thrust available.

2H4
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Jetlagged
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RE: Boeing 747-400 Reverse Thrust?

Thu Mar 27, 2008 8:29 pm



Quoting Speedracer1407 (Reply 43):
Strange that you would use the Little Rock accident, in which the plane veered off the runway with fatal consequences, as evidence that differential reverse can be "extremely effective in steering the aircraft or helping to keep it on the runway."

On an aircraft like an MD80 with tail mounted engines full reverse thrust will significantly reduce directional control from the fin and rudder. The amount of reverse applied was criticised in the NTSB report (too much to maintain directional control) and they commented that when reverse thrust was stowed briefly during the landing roll directional control was restored.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
kimberlyRJ
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RE: Boeing 747-400 Reverse Thrust?

Sat Mar 29, 2008 3:22 pm



Quoting Starlionblue (Reply 40):
"the other way around" would be that braking replaces reverse? Yes it can, as evidenced by the large number of aircraft without reversers

Talking about large aircraft here (topic of B744) and I don't know any that are not fitted with reverse thrust of some type (I mean all 'heavy' aircraft.

Quoting 2H4 (Reply 44):
All it takes is one section of runway with poor to nil braking to see the value in having reverse thrust available.

Quite, something that happens more then passengers think, well nil to little. Even if nil breaking happens for just a few seconds thats a lot of stopping distance lost.

Quoting Jetlagged (Reply 45):
On an aircraft like an MD80 with tail mounted engines full reverse thrust will significantly reduce directional control from the fin and rudder. The amount of reverse applied was criticised in the NTSB report (too much to maintain directional control) and they commented that when reverse thrust was stowed briefly during the landing roll directional control was restored.

I used the Littlerock incident as I had saw a report into it, where the now retired head of the NTSB said that reverse thrust “is a good use of directional control in certain situations”. In concern of the design of the MD80 types I can see the point with the engines.

Asking the Boeing 744 Senior Captain (he was the flying pilot on my return flight from JFK) he said that they often use different amounts of reverse thrust of each engine, and if they were leaving the runway unexpectedly it would be one of the main, most important and useful resources they would turn to.

Slightly off topic my feet are killing me, why did they make T5 so big, been helping people PAX (and crew) find their way to the gates, and getting lost myself - not good! GRR  Sad

Hope everyone is having a great weekend

Kimberly.
 
Bellerophon
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RE: Boeing 747-400 Reverse Thrust?

Sat Mar 29, 2008 6:07 pm

I regret to say that much of what has been written about the use of reverse thrust on landing in general, and BA's B747 reverse thrust SOPs in particular, is completely wrong.


...Noticed that when landing at LHR the pilots normally use all four engines in reverse, but on the other hand at foreign airports such as Africa and South America we tend to use reverse on 2 and 3 only…

I've been landing B747s in Africa and South America for the last thirty years. I've never seen that.


...on the Boeing 747 having four engines able to reverse, if there were issues keeping the aircraft on the runway the pilots could not only use differential breaking (gear) but also one (or two or three engines) in reverse to help turn the aircraft suddenly or effectively....

Non standard, and highly likely to be ineffective, if not counter-productive.


...When I was on the flight deck on a flight landing at MIA during a really heavy rain storm and high cross winds and the pilots engaged reverse on engine 3 and then about four seconds after engine 2 then about five seconds after that engines 1 and 4 at the same time, each seems to have an effect on ‘steering’ the Boeing 744 and put the nose straight on the centre line....

Unbelievable.

If that happened, not only is it non-standard and unnecessary, but - in the conditions you describe - it could also be dangerous. When the SESMA tapes are run, the Captain can expect to be asked for a satisfactory explanation by the SESMA rep. Without one - and I can't think of one off-hand - he could be in serious trouble, BA have SOPs for a reason, and they enforce their use. If a F/O on my flight did this on landing, he would be suspended.


...Asking the Boeing 744 Senior Captain (he was the flying pilot on my return flight from JFK) he said that they often use different amounts of reverse thrust of each engine...

I'm not sure who you mean by "the Boeing 744 Senior Captain", but whoever said this, if they said it, they're talking rubbish.


Sorry, I don't believe any of it!

Bellerophon
 
lowrider
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RE: Boeing 747-400 Reverse Thrust?

Sat Mar 29, 2008 6:27 pm



Quoting Kimberlyrj (Reply 36):
When I was on the flight deck on a flight landing at MIA during a really heavy rain storm and high cross winds and the pilots engaged reverse on engine 3 and then about four seconds after engine 2 then about five seconds after that engines 1 and 4 at the same time, each seems to have an effect on 'steering' the Boeing 744 and put the nose straight on the centre line.

Did they actually articulate the thrust reversers that way, or did the engines just not spool up together? The the only time time I have seen the outboard reversers intentionally not used was at an airport that had a NOTAM warning of unexploded ordinance in all unpaved portions of the airport.
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hotelmode
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RE: Boeing 747-400 Reverse Thrust?

Sun Mar 30, 2008 10:26 am

Thank goodness you replied Bellerophon, I didnt recognise any of those techniques in our SOPs either! I've never seen anything above idle reverse used at LHR either.

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