Reverse thrusts
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Mutt: re DC-8's... yessir, inboards are used to drop out of the skies for emerg. descent (but NOT used for ducking back to the glide when turned onto finals too early!!). 
BN2A: You are bang on about using idle reverse only when one is locked out... of course many of us have been guilty of briefing "Idle reverse only on the good one" then after a long duty-day / long block of min rests...we still slam them into full reverse with a "AHHH CR@P!" then correct ourselves by zipping it back to idle with nothing harmed but our foreheads from smacking one's self for the boo-boo...
Cheers,
Ray Darr
BN2A: You are bang on about using idle reverse only when one is locked out... of course many of us have been guilty of briefing "Idle reverse only on the good one" then after a long duty-day / long block of min rests...we still slam them into full reverse with a "AHHH CR@P!" then correct ourselves by zipping it back to idle with nothing harmed but our foreheads from smacking one's self for the boo-boo...
Cheers,
Ray Darr
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... although probably a tad politically incorrect ... it's a wonderful sensation when one rips in a fistful of reverse after touchdown ... almost as good as .. no ... we aren't allowed to use old technology engines any more, are we ... ?
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.... and especially so when the runway lights whites have turned to red & white, and even more so when they've all become red, and / or the runways wet / slippery and all you're thinking is..... "Ohhhhh sh#t, come on, stop you bugger !!!" 
Transparency International
Last edited by dusk2dawn; 20th Feb 2005 at 16:06.
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The IL 62 is an older generation aircraft. Look you is correct about the 737 allowing the reversers to deploy at 10 feet radalt. However that part of the 737 design has been carried forward to the later 737's, including the NG. Therefore the 737 reverser design is essentially older generation as well from the 100 and 200 series. I think if you look again at my post I did say modern civil jet airliners.
The Trident could also deploy reversers just before touchdown (10 feet is at or pretty damn close to touchdown) and frequently did so for short runways such as Aberdeen and Milan Linate. The latest design of commercial jet aircraft use the air/ground safety sensor (or squat switch) to allow deployment of the reversers.
The Trident could also deploy reversers just before touchdown (10 feet is at or pretty damn close to touchdown) and frequently did so for short runways such as Aberdeen and Milan Linate. The latest design of commercial jet aircraft use the air/ground safety sensor (or squat switch) to allow deployment of the reversers.
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Remember that the thrust reversers are most effective at high speeds. Same goes for the Spoilers.
At my airline we try and keep the use of brakes to a minimum. This is because our turnaround times are so short. If brakes are used excessively on landing our Vmbe maybe exceeded for take off. Thus when the day comes to hit the brakes, they overheat and 'brake fade' becomes more than a couple of lines in the training manual!!!
At my airline we try and keep the use of brakes to a minimum. This is because our turnaround times are so short. If brakes are used excessively on landing our Vmbe maybe exceeded for take off. Thus when the day comes to hit the brakes, they overheat and 'brake fade' becomes more than a couple of lines in the training manual!!!
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Mutt: Required landing charts for dry runways do not include reverse thrust. This is a certification rule. Reverse thrust is only included in contaminated runways. In the Lauda case i think that the problem was not the reverser deploying but the fact that the engine was running at high N1 when the reverser deployed. When manually activating reverse you first go to idle thrust which I don´t beleive would cause a problem in flight. However as the reverser in the Lauda flight extended by itself it did so at a high thrust setting causing interupted airflow over a section of the wing as well as developing a significant yaw.
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Md-driver
Required landing charts for dry runways do not include reverse thrust That is very true, however those nice people in Seattle publish a B747 graph with required stopping distances based on different configurations!
Point taken about the Lauda, thanks.
Mutt.
Required landing charts for dry runways do not include reverse thrust That is very true, however those nice people in Seattle publish a B747 graph with required stopping distances based on different configurations!
Point taken about the Lauda, thanks.
Mutt.
Reverse
Didn't Lufthansa have an A320 that overran with fatalities due to
the inability of the pilot flying to activate reverse or deploy spoilers due to air/ground sensing thinking the aircraft was still airborne.
the inability of the pilot flying to activate reverse or deploy spoilers due to air/ground sensing thinking the aircraft was still airborne.
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Flap5
The later versions of the 737 have the CFM56 engine and therefore have a cascade style of reverser. The JT8 versions had the bucket/target style. Whether or not the reversers can be used in flight is down to two things:
1. Was the airframe / reverser combination certified using controllability (sp?) - if so, then the structure supporting the TR is stressed to take flight loads with full power deployment and flight testing has proven the controllability of the deployed TR / airframe combination
or 2. was the system cerified using system redundancy to ensure no inadvertant deployment. If this method is used, the structure is not generally designed to take inadvertant in-flight deployment loadings. The likelyhood of in flight deployment has been mitigated to such a small number by the use of a multitude of interlocks that to carry sufficient structure around is not efficient nor required.
As an aside:
Does anyone know of other military fast jets (apart from the Tornado) that have thrust reversers??
The later versions of the 737 have the CFM56 engine and therefore have a cascade style of reverser. The JT8 versions had the bucket/target style. Whether or not the reversers can be used in flight is down to two things:
1. Was the airframe / reverser combination certified using controllability (sp?) - if so, then the structure supporting the TR is stressed to take flight loads with full power deployment and flight testing has proven the controllability of the deployed TR / airframe combination
or 2. was the system cerified using system redundancy to ensure no inadvertant deployment. If this method is used, the structure is not generally designed to take inadvertant in-flight deployment loadings. The likelyhood of in flight deployment has been mitigated to such a small number by the use of a multitude of interlocks that to carry sufficient structure around is not efficient nor required.
As an aside:
Does anyone know of other military fast jets (apart from the Tornado) that have thrust reversers??
The 767 you were sat in will have used idle reverse and autobbrakes. Modern carbon brakes work better when hot and wear out quicker when the application is applied more than once and/or varied. BF Goodrich (the manufacturer od the majority of carbon brake systems) state that the reccomended technique is to use autobrake and idle reverse. Autobrake sets a decelleration rate measured by the inertial reference system rather than a brake pressure (unless you use setting MAX or RTO where you get the full system pressure).
For example, setting 3 on a 747-400 gives you a rate of 4 feet per second per second and if you bring the reversers up above idle after touchdown, by the time you have spooled the engine up in reverse the brakes would have already been pressurised and the system will reduce the pressure to maintain the decceleration rate. When you stow the reversers, the brakes will modulate again, so you have three changes in braking rather than one thus wearing out the brakes more, making more noise and putting more stress on the engines.
I think the SAAB Viggen has reverse thrust as well.
For example, setting 3 on a 747-400 gives you a rate of 4 feet per second per second and if you bring the reversers up above idle after touchdown, by the time you have spooled the engine up in reverse the brakes would have already been pressurised and the system will reduce the pressure to maintain the decceleration rate. When you stow the reversers, the brakes will modulate again, so you have three changes in braking rather than one thus wearing out the brakes more, making more noise and putting more stress on the engines.
I think the SAAB Viggen has reverse thrust as well.
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PT6ER,
Engine type is irrelevant. It is how the reversers are activated that matters. Both the JT8D powered 200 series and the CFM56 powered 300 and NG series have reversers activated by 10 foot radalt or the air/ground safety sensor. Your point is spurious and irrelevant.
Engine type is irrelevant. It is how the reversers are activated that matters. Both the JT8D powered 200 series and the CFM56 powered 300 and NG series have reversers activated by 10 foot radalt or the air/ground safety sensor. Your point is spurious and irrelevant.
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Flap5
Sorry for deigning to disagree with you but, and I quote,
"Therefore the 737 reverser design is essentially older generation as well from the 100 and 200 series. I think if you look again at my post I did say modern civil jet airliners."
The design of the reverser is most definately not "older" by which you meant (I thought) a target type.
I was not commenting on the design of the control architecture (SP?) although the safety interlocks required on modern reversers far exceed anything used in the past (I think the Lauda Air incident drove a lot of the changes). It is interesting to note that some modern target type reversers (and I have worked on the design and certification of three so far) are aerodynamically unable to deploy above a pre-determined power setting. Some bizjets are certified using controllability and some using system redundancy - horses for courses really
My comments are not spurious nor irrelevant and were left as an addition to a good thread, not as any personal jibe. Calm down and re-read my post.
Remember the "Word" according to Bruce Hornsby.....
"That's just the way it is"
Sorry for deigning to disagree with you but, and I quote,
"Therefore the 737 reverser design is essentially older generation as well from the 100 and 200 series. I think if you look again at my post I did say modern civil jet airliners."
The design of the reverser is most definately not "older" by which you meant (I thought) a target type.
I was not commenting on the design of the control architecture (SP?) although the safety interlocks required on modern reversers far exceed anything used in the past (I think the Lauda Air incident drove a lot of the changes). It is interesting to note that some modern target type reversers (and I have worked on the design and certification of three so far) are aerodynamically unable to deploy above a pre-determined power setting. Some bizjets are certified using controllability and some using system redundancy - horses for courses really
My comments are not spurious nor irrelevant and were left as an addition to a good thread, not as any personal jibe. Calm down and re-read my post.
Remember the "Word" according to Bruce Hornsby.....
"That's just the way it is"
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Ah! I sensed that. 
There was that natural antagonism that exists between a pilot and an engineer! I usually get airborne in an aircraft just after an engineer has 'fixed' a problem only to find it reoccur. I get this irrational urge to shake the engineer warmly by the throat! 
By the way I tried to post yesterday but the site had crashed. Obviously an engineer had been let loose on it!
There was that natural antagonism that exists between a pilot and an engineer! I usually get airborne in an aircraft just after an engineer has 'fixed' a problem only to find it reoccur. I get this irrational urge to shake the engineer warmly by the throat! By the way I tried to post yesterday but the site had crashed. Obviously an engineer had been let loose on it!
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Last Words
Reverser's Deployed!!
First Officer Josef Thurner, Air Lauda 004
Last recorded words during "impossible" in-flight ddeployment
of the B-767's Reverser
26th may 1991
obviously not a good thing!
First Officer Josef Thurner, Air Lauda 004
Last recorded words during "impossible" in-flight ddeployment
of the B-767's Reverser
26th may 1991
obviously not a good thing!
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Don't know about large civil aircraft, however, I once saw a Lear 25 landing at Columbia airport in California with his reversers half deployed at approx 1/2 mile final and 400 AGL. Have a feeling this was NOT something found in the aircraft's POH.
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They are designed to but they do it??
Hi PT6ER I worked in an Airline that the reverse (probably one of those you worked on the project) was designed to never open for aerodinamic reasons below 200kts once airborne in case of squatch switch failure so how come it did opened and killed 99 people 94 on the airplane and 5 on ground just after rotate at about 150kts or less?
So my point is and I think that is what the other guys try to say is, they fail because there is no perfect system as there is no perfect human.
I agree they don't fail very often but they do fail and as far as I know the Lauda Air case nothing was done just the fact of PW4000 lost theyr certification to use reverse in flight as speed brakes therefore deactivated this function.
So my point is and I think that is what the other guys try to say is, they fail because there is no perfect system as there is no perfect human.
I agree they don't fail very often but they do fail and as far as I know the Lauda Air case nothing was done just the fact of PW4000 lost theyr certification to use reverse in flight as speed brakes therefore deactivated this function.
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B737 repuires BOTH gates to be open: 10 ft RadAlt AND the squat/weight switches to be made. Reverser deployment in the air is unavailable, prohibited if it were, and undesirable on any account.