DIA
Topic Author
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Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 12:48 am

Is/Was this a common practice?
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Or is/was it common with the 707s/DC-8s maybe?

I seem to remember some DC-10s doing this. . .that I've seen. . .

DIA

[Edited 2003-04-21 17:49:58]
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JBirdAV8r
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 3:03 am

You lose speed a bit faster when doing that, and it also gives you a bit more directional control with the rudder I believe. In smaller planes (with no spoilers) it puts more weight on the wheels so your brakes are more effective.

I've seen this done several times. I saw it last on a United 737-322. However, all the airplanes were empty.
I got my head checked--by a jumbo jet
 
fritzi
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 3:14 am

I think its up to the pilots to choose when they deploy the reverse thrust but the spoilers will deploy as soon as there is weight on the Main gears if the spoiler lever is set to auto.

Here are some pics of reverse thrust+spoiler+high nose gear


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Photo © Paul Morley



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Photo © David Morrell
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Photo © Tony Zeljeznjak

 
JBirdAV8r
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 3:16 am

Fritzi, you are correct. I don't believe there is a set practice for this.

I know it's a bigger deal on airplanes with rear-mounted engines because reverse thrust has an effect on the nose height (the DC-10 comes to mind right off the bat)
I got my head checked--by a jumbo jet
 
MxCtrlr
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 3:19 am

Even back with the old 707's, the speedbrakes (spoilers), when armed, automatically deploy as soon as the weight is on the gear (squat switch is set) and the wheel spin up (so as to assist the braking action). Thrust reversers are, like stated above, Captain's discretion but usually deployed as soon as the speedbrakes deploy (speedbrake handle moves aft).

MxCtrlr  Smile/happy/getting dizzy
Freight Dogs Anonymous - O.O.T.S.K.  Smokin cool
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fritzi
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 3:21 am

A little correction for my previous post before some nit picky 14 year old points it out:

...weight on the Main gears if the spoiler lever is set to arm.
 
Jason McDowell
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 3:32 am



The following is from the Boeing 737 Flight Crew Training Manual:


"Avoid touching down with thrust above idle since this may establish an airplane nose up pitch tendency and will increase landing roll.

If the speedbrakes do not extend automatically, after the airplane settles onto the runway, move the speedbrake lever into the UP position, and initiate reverse thrust. Fly the nosewheel down to the runway smoothly by relaxing aft control pressure. Do not attempt to hold the nosewheel off the runway. Holding the nose up after touchdown for aerodynamic braking is not an effective braking technique.

To avoid the risk of tailstrike, do not allow the pitch attitude to increase after touchdown. However, applying excessive nose down elevator during landing can result in substantial forward fuselage damage. Do not use full down elevator. Apply wheel brakes smoothly with steadily increasing pedal pressure as required for runway condition and runway length available. Maintain deceleration rate with constant or increasing brake pressure as required until stopped or desired taxi speed is reached."


- JM




 
m717
Posts: 540
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 4:00 am

On the 717, the thrust reversers cannot be deployed until the nose gear is on the ground. They are locked out until the "ground shift mechanism", which is a weight on wheels type switch on the nose gear, senses that the aircraft is in the "ground" mode.
 
cedarjet
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 4:16 am

M717, you said re the "Boeing" 717 that reverse thrust is locked out on landing due to a "a weight on wheels type switch on the nose gear". Other aircraft have this (not the DC8, which used reverse thrust in the air for a fast descent); but surely not the NOSE gear?
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
 
DIA
Topic Author
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 4:32 am

Very interesting stuff guys. Thanks, and I'll keep reading up.

Does any other a/c have the 717-type precaution of "ground mode"?

DIA
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N79969
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 4:36 am

I believe that the air/ground mode sensor is common. If I recall correctly, one of the factors that caused the 1991 Lauda Air 767 crash was a fault in that circuit. The reverser opened up in flight.
 
m717
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 4:37 am

Cedarjet,

That is correct. On the B717, the lockout for the thrust reversers is part of the "ground shift" mechanism. There are various functions on the ground shift, and depend on whether the mechanism senses the aircraft is in the "air" or "ground" mode. Pressurization and landing gear handle are a couple. Thrust reversers are another one. They are locked out until the ground shift senses the aircraft is in the "ground" mode, and the ground shift mechanism is on the nose gear. If you ever have the chance to look closely at a 717 nose gear assembly, the ground shift mechanism is a large spring device on the aft portion of the assembly.

[Edited 2003-04-21 21:38:45]
 
Boeing Nut
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 5:26 am

Otherwise known as aerodynamic braking!  Laugh out loud
I'm not a real aeronautical engineer, I just play one on Airliners.net.
 
m717
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 5:58 am

Cedarjet,

One more thing. The "Boeing" 737-100 and -200 basic also had mechanical lockouts on the thrust reversers (you couldn't pull the thrust levers into the reverse position) until the NOSEWHEEL was on the ground. So, I guess the "wretched" 717 isn't the only "Boeing" with this feature. Sorry to disappoint.
 
FutureFO
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 6:44 am

The only time this is done in the US is pretty much when a heavy is landing on a short runway and need the extra touch to slow down. But there is no set practice to doing it.
I Don't know where I am anymore
 
CX Flyboy
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 9:39 am

When we land, we always land with full flaps and the speed brakes armed. Upon touchdown, we would be in a fairly nose high position, especially on the 777-200 (Compared to the 777-300). Upon touchdown, we also reach for the reversers immediately. However, we do not practise aerodymanic braking by holding the nose up in the air. The problem is when the nose is held too high, either you can lessen the weight on the wheels, and/or when the aircraft slows enough and you don't lower the nose to the ground slowly, it smacks onto the ground causing discomfort and possible damage to the nose area. Our company seriously discourages this sort of practise. Instead, after landing we are to gently, but fairly promptly lower the nose to the ground. This also helps with steering as the aircraft slows.
 
JETPILOT
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 9:52 am

On lightly loaded flights such as I had the other night (727) I popped the spoilers and threw it into reverse thrust when the mains touched, I got 3 lights and I brought the thrust levers up to the second notch of reverse, about 1.93 EPR and the nose will definetly rise unless moderate foward pressure is kept on the yoke. It freaks out new FO's who havent landed light before.

JET

[Edited 2003-04-22 02:53:30]
 
goboeing
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 9:59 am

While the discussion about reverse thrust is active, I have 2 questions:

-Regarding JET's post above, does the engine have several different set "levels" of thrust for reverse, or is it free flowing like it is in forward producing thrust modes?

-When the reverse thrust is at idle, do the reverser panels or whatever they are called still go to the full deployed position, or do they need a little more reverse thrust to go out all the way? Basically, can they be put at say halfway, or are they always either in or out?

Nick
 
JETPILOT
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 10:03 am

The DC8 has a ground shift mechanism....

On the DC8 WITH THE GEAR DOWN only in flight idle thrust uavailable until the ground shift mechanism is compressed. Once compressed max continuous thrust is avaialable. And yeah its on the nose gear.

The procedure in the DC8 for landing is to get the plane firmly on the ground to prevent a main gear spoiler lockout situation which can happen during a soft touchdown. If that happens your spoilers wont automaticly deploy. Then smash the nose gear into the runway to get the ground shift compressed so you can use the marginally effective reversers if they ever open at all.

The 8 was fun !!

JET



 
JETPILOT
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 10:08 am

The 727 has 2 reverse detents used as a reference only. Any range of reverse thrust is available.

The reversers can be in 2 positions... open or closed.

JET

[Edited 2003-04-22 03:09:40]
 
411A
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Tue Apr 22, 2003 3:07 pm

MxCtrlr,

Interesting comments about the B707. Which particular model had auto spoilers?
As I personally flew the aeroplane for ten years, don't remember any models equipped as you describe.
Which particular model of the 707 are you referring? Big grin
 
Ljungdahl
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Wed Apr 23, 2003 12:31 am

DIA,

Thanks, mate, for plugging my photo!!  Big thumbs up

While on the subject about use of thrust reversers (sorry if this had been covered earlier in this thread), I have observed frequently in the past that the IL-62 usually had a practice to engage reverse thrust even BEFORE touchdown!

(...sorry, one more plug, but I think this is related to this topic...)  Big grin

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Johan (Ljungdahl)

 
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Wed Apr 23, 2003 12:43 pm

I always have used the technique of landing nose up, reversers (thrust as required) flaps and spoilers/speed brakes on the 747 I currently fly, as well as the 707 and 727, same technique... I land on many runways without hard brakes use... most of the time (747) I only start using the brakes when down to 60 knots or even much lower speed, thanks to reversers and all aerodynamic braking.
xxx
With the DC8 it is better to land and let nose down early... I flew the DC8s as well, but keeping the nose high after touch down on a long DC8-60 or 70 can easily result in a tail strike... I used to do it in the 62s which have shorter fuselage.
xxx
Never heard of auto spoilers in 707s... I flew all major versions of these, 100s, 300 and 720s... none had automatic spoilers/speed brakes, sorry.
xxx
Happy contrails to you all  Smile
(s) Skipper
 
AJ
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Wed Apr 23, 2003 2:41 pm

The 767 has several features that can cause pitching on landing.
First of all the inboard ailerons droop with flap settings of 5 or more to 'flatten' the approach attitude.
The big supercritical wing enters ground effect at about 300'AGL, meaning more nosedown is required to fly to the touchdown zone.
On main gear touchdown the (armed) speedbrake deploys causing a nose up pitch moment.
The autobrakes then engage causing a nosedown pitch.
Due to the engine's forward mounting deploying the reversers causes a decrease in airflow over the wing and an associated nosedown pitch.
Flying the nosegear onto the runway is an art! If not done properly it can cause an embarrassing CLUNK as the nosegear contacts the runway, or worse as an American Airlines B767-300 crew found when they buckled their aircraft just forward of the wing.
http://www.aaib.dft.gov.uk/bulletin/oct99/n373aa.htm

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jetskipper
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RE: Reverse Thrust/Full Flaps/Spoilers W/Nose Up High!

Fri May 02, 2003 1:58 pm

On the EMB-145 we deploy the "buckets" as soon as we have main wheel touchdown, it serves not only to aid in slowing, but also to slow the nose from pitching down rapidly as it tends to do as the speedbrakes are deployed. Even though the buckets may be deployed the N1 is prevented from increasing until there is weight on the nosewheel.

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