Forward Slipping a 737-800
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dvt
YIKES ! 30yrs of flying transport aircraft here. That is one manuever I've never seen and hope I never do. I would
respectfully suggest you consider limiting forward slips to
light aircraft and gliders.
That swept wing airplane you are flying can and will do strange
things to you when you least expect it. Fly it like you were taught.
, and it will treat you nicely.
YIKES ! 30yrs of flying transport aircraft here. That is one manuever I've never seen and hope I never do. I would
respectfully suggest you consider limiting forward slips to
light aircraft and gliders.
That swept wing airplane you are flying can and will do strange
things to you when you least expect it. Fly it like you were taught.
, and it will treat you nicely.
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Slips
dvt is a little irritating. There are two possibilities, it seems to me.
(1) dvt is confident of being right. I.e. it's all right to slip a 737-800 to lose altitude nearing a runway. In which case he just does it, and is confident of not having to explain his actions to a supervisor.
(2) dvt is not confident of being right. In which case he would be hostile and oversensitive in responding to the expressed reservations and concerns of most of the other posting members of PPRUNE.
Obviously (2) fits the data better than (1).
Now as to the merits of the quite interesting issues dvt raises.
(1) Nothing should interfere with the stabilized approach concept for largish jets. A slip (in such an airplane) is a not good idea below 1,500 feet. Surely that's a fair comment.
(2) There are slips and there are slips. Full deflection of a rudder are a really stupid idea in a swept wing jet. Light or moderate deflection with enough cross-control on ailerons, might be fine. Don't know. More to the point, neither does dvt. Is he comfortable with discussing "crossover" speed etc?
(3) If ATC gives you "crap" vectors, etc, presumably one has the ability to either dirty up or slow up. That way the "crap" vectors aren't as "crap" since the turn radius is tighter. Hence, no need for the heroics at the bottom of the approach.
(4) Many airline and jet pilots do aerobatics for fun. In an airplane designed for it. Treating a passenger jet differently (and more conservatively) is hardly effeminate.
(5) dvt needs to be counseled by his Professional Standards Committee. It's not his colleagues' job to justify their discomfort with slipping a transport jet. It's his job to justify doing it (in the absence of a compelling need to do it, or in the absence of an emergency).
(6) A Captain can do absolutely whatever needs doing in an emergency i.e. no engines, smoke in cockpit, etc. Slipping is one such thing. But when the aircraft is otherwise in fine shape, I just can't see slipping on a regular basis. That one's testosterone permits one to do it is not sufficient explanation.
(1) dvt is confident of being right. I.e. it's all right to slip a 737-800 to lose altitude nearing a runway. In which case he just does it, and is confident of not having to explain his actions to a supervisor.
(2) dvt is not confident of being right. In which case he would be hostile and oversensitive in responding to the expressed reservations and concerns of most of the other posting members of PPRUNE.
Obviously (2) fits the data better than (1).
Now as to the merits of the quite interesting issues dvt raises.
(1) Nothing should interfere with the stabilized approach concept for largish jets. A slip (in such an airplane) is a not good idea below 1,500 feet. Surely that's a fair comment.
(2) There are slips and there are slips. Full deflection of a rudder are a really stupid idea in a swept wing jet. Light or moderate deflection with enough cross-control on ailerons, might be fine. Don't know. More to the point, neither does dvt. Is he comfortable with discussing "crossover" speed etc?
(3) If ATC gives you "crap" vectors, etc, presumably one has the ability to either dirty up or slow up. That way the "crap" vectors aren't as "crap" since the turn radius is tighter. Hence, no need for the heroics at the bottom of the approach.
(4) Many airline and jet pilots do aerobatics for fun. In an airplane designed for it. Treating a passenger jet differently (and more conservatively) is hardly effeminate.
(5) dvt needs to be counseled by his Professional Standards Committee. It's not his colleagues' job to justify their discomfort with slipping a transport jet. It's his job to justify doing it (in the absence of a compelling need to do it, or in the absence of an emergency).
(6) A Captain can do absolutely whatever needs doing in an emergency i.e. no engines, smoke in cockpit, etc. Slipping is one such thing. But when the aircraft is otherwise in fine shape, I just can't see slipping on a regular basis. That one's testosterone permits one to do it is not sufficient explanation.
All,
For those of you a trifle reticent about “slipping” him bigfella balus, all B757/767/744 on an autopilot coupled approach, below 500 ft, handle cross wind by side/forward slipping ( take your choice) admittedly in the case of the B744 a combination of crab and side slip.
A B767 is all sideslip with the aircraft centreline aligned with the runway below 500’, in a max (A/P) crosswind the wing down is about 7 degrees, and it does it beautifully.
As for D.P Davies, with all due respect to his fans, I would strongly suggest you take some of his pronouncements with a grain of salt, in fact he had very limited experience on large aircraft, but that did nothing to moderate his views.
He also had a highly developed "not invented here" complex, that was not trans Atlantic limited, it also applied cross Channel. The Caravel was never certified in UK, ( the forward fuselages were originally built by Dh).
Furthermore, aircraft handling characteristics have improved greatly since the late 50’s and early 60’s, just fly your current party transport to it’s sops, not according to Dai Davies.
Quite frankly, some of the modification demanded to B707-300/320 on the G- register (non Boeing stab trim settings for T/O, modifications to the spoiler isolation system to solve a non problem, but making handling jam stab procedures far more difficult, stick pushers for aircraft that DID NOT deep stall, to name three) seriously degraded the safe handling of these aircraft. A stick pusher going off in the flare in strong gusty cross winds made for some interesting moments.
If my memory serves me correctly, for some time he would not even permit the use of Flap 50 for landing in the early BOAC 707. The claim was that the aircraft had a slight pitch up, before the nose pitched down, in a Flap 50 stall. This was quite true, it did, the slightest little nibble, but by that time the airframe buffet bordered on the frightening, there was no shortage of natural warning, quite apart from the fact that the stick shaker was also going crazy. But the fact remained, the nose always fell through.
I often wonder by how much we shortened the airframe lives of these aircraft in this kind of training ?? But it seemed like a good idea at the time. To my mind, given that any pilot doing this kind of type rating was already an experienced pilot, approaching stall buffet would have been enough, without doing full stalls.
AAAAAH !!, the Good Old Days. !!!
Tootle pip !!
For those of you a trifle reticent about “slipping” him bigfella balus, all B757/767/744 on an autopilot coupled approach, below 500 ft, handle cross wind by side/forward slipping ( take your choice) admittedly in the case of the B744 a combination of crab and side slip.
A B767 is all sideslip with the aircraft centreline aligned with the runway below 500’, in a max (A/P) crosswind the wing down is about 7 degrees, and it does it beautifully.
As for D.P Davies, with all due respect to his fans, I would strongly suggest you take some of his pronouncements with a grain of salt, in fact he had very limited experience on large aircraft, but that did nothing to moderate his views.
He also had a highly developed "not invented here" complex, that was not trans Atlantic limited, it also applied cross Channel. The Caravel was never certified in UK, ( the forward fuselages were originally built by Dh).
Furthermore, aircraft handling characteristics have improved greatly since the late 50’s and early 60’s, just fly your current party transport to it’s sops, not according to Dai Davies.
Quite frankly, some of the modification demanded to B707-300/320 on the G- register (non Boeing stab trim settings for T/O, modifications to the spoiler isolation system to solve a non problem, but making handling jam stab procedures far more difficult, stick pushers for aircraft that DID NOT deep stall, to name three) seriously degraded the safe handling of these aircraft. A stick pusher going off in the flare in strong gusty cross winds made for some interesting moments.
If my memory serves me correctly, for some time he would not even permit the use of Flap 50 for landing in the early BOAC 707. The claim was that the aircraft had a slight pitch up, before the nose pitched down, in a Flap 50 stall. This was quite true, it did, the slightest little nibble, but by that time the airframe buffet bordered on the frightening, there was no shortage of natural warning, quite apart from the fact that the stick shaker was also going crazy. But the fact remained, the nose always fell through.
I often wonder by how much we shortened the airframe lives of these aircraft in this kind of training ?? But it seemed like a good idea at the time. To my mind, given that any pilot doing this kind of type rating was already an experienced pilot, approaching stall buffet would have been enough, without doing full stalls.
AAAAAH !!, the Good Old Days. !!!
Tootle pip !!
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Hope I'm not being pedantic here Ledsled, but the B767 manual states "A/P systems initiate a slip with a maximum bank angle of 2 degrees when the crab angle exceeds 5 degrees"
There is a considerable difference between two degrees and seven. Also, the autopilot will be completely stabilised on the G/P and localiser, on speed and spooled up when executing it.
The other problem with sideslipping a swept wing aircraft is of course that the apparent airflow to the leading wing is much greater than it is to the trailing wing. If you have enough slip at low airspeed, I would imagine you could find yourself with an unexpected wingdrop.
Any expert comments on this?
There is a considerable difference between two degrees and seven. Also, the autopilot will be completely stabilised on the G/P and localiser, on speed and spooled up when executing it.
The other problem with sideslipping a swept wing aircraft is of course that the apparent airflow to the leading wing is much greater than it is to the trailing wing. If you have enough slip at low airspeed, I would imagine you could find yourself with an unexpected wingdrop.
Any expert comments on this?
Bottums Up
Referring to the link explaining the difference between a side slip and a forward slip, and to some of the posts trying to explain the difference, I can't see any difference, except that in the so called side slip, the amount of slip will usually be limited to that amount needed to off set drift. Whereas the so called forward slip is limited by rudder v aileron/roll spoiler authority and the size of the pilot's gonads.
The aircraft doesn't know or care which way the wind is blowing, both manoeuvres involve crossed controls and a flight path into the lower wing.
For my money, they're one in the same manoeuvre.
The aircraft doesn't know or care which way the wind is blowing, both manoeuvres involve crossed controls and a flight path into the lower wing.
For my money, they're one in the same manoeuvre.
Bally Heck,
With all due respect, read a little further ---- at 500 agl, the A/P “kicks” off the drift, and from there to touchdown it is all sideslip, the numbers you have quoted are very close to what the 744 does under the same circumstances.
Would anybody like to comment on the L-1011 A/P coupled in a cross wind, I seem to recall it had a much higher A/P coupled limit than the 767 or the 744, which is 26 kt or so.
Tootle pip !!
With all due respect, read a little further ---- at 500 agl, the A/P “kicks” off the drift, and from there to touchdown it is all sideslip, the numbers you have quoted are very close to what the 744 does under the same circumstances.
Would anybody like to comment on the L-1011 A/P coupled in a cross wind, I seem to recall it had a much higher A/P coupled limit than the 767 or the 744, which is 26 kt or so.
Tootle pip !!
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LeadSled
At the risk of going slightly off thread and also of repeating myself, I quote from the B 767 vol 2
ROLLOUT mode engages at 5 foot R/A so the aircraft will probably still be wing down at touchdown.
It does not at any time "kick" off the drift, and from the way I read it, a crab angle of much greater than 5 degrees would result from a strong crosswind once tha A/P had adjusted to 2 degrees bank angle. That however would probably happen at crosswinds outside the certificated limit for autoland.
At the risk of going slightly off thread and also of repeating myself, I quote from the B 767 vol 2
The (runway align) submode operates as follows:
- actuated at 500 feet RA with LAND 3 or LAND 2 annunciated.
- activation not displayed
- A/P system initiates a slip with a maximum bank angle of 2 degrees when the crab angle exceeds 5 degrees
- Wing levelling from the slip is initiated when the ROLLOUT mode is engaged
- actuated at 500 feet RA with LAND 3 or LAND 2 annunciated.
- activation not displayed
- A/P system initiates a slip with a maximum bank angle of 2 degrees when the crab angle exceeds 5 degrees
- Wing levelling from the slip is initiated when the ROLLOUT mode is engaged
It does not at any time "kick" off the drift, and from the way I read it, a crab angle of much greater than 5 degrees would result from a strong crosswind once tha A/P had adjusted to 2 degrees bank angle. That however would probably happen at crosswinds outside the certificated limit for autoland.
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Hey Gang,
Notch Johnson here. I've been away the past few days, with my girl BJ, slipping her other things besides airplanes. She likes to slip out to the country and ride the baloney pony with me. Anyways, I'm back and I'm truly astounded at the response of this thread. Though I think it has more to do with my charming personality than anything else. Right? I didn't want to discuss the merits of a simple flight maneuver, but you are right...I don't own this thread. So forgive me. Ok then.
Here's an excellent question on reader’s minds, submitted by Mouse...
"For the benefit of my curiosity when would you envisage needing this particular 'trick'?"
Well readers here my short response….”When going around is not the BEST option”.
I can hear you all now...."GASP! Oh the Horror! Murmur! Are you mad, man! Going around is ALWAYS the best option!" I’m my opinion; this is not always the case. Let me explain. It seems to me, many of you may only be familiar with flying into “flat and rolly" places like LHR. You can be forgiven for holding the view that Going Around is always superior to slipping it in. However, let me take you into some of the "Salad Bowls of Terrain" in places like Central/South America and the Caribbean. These places are scary enough in the daytime; try a visit at night. Many of these places have some of the most complicated and insane "Missed Approach" procedures you could imagine. Their "Engine-Out Missed Approach" procedures are even worse! You look at them and you say ..."You've got to be joking me! Right!" It looks like they were developed to satisfy some legal requirement knowing full well that Chuck Yeager might not be able to pull it off.
Anyways, case in point. I'm flying into one of these "Salad Bowls". I see that I'm high by a couple of thousand feet. I'm fully configured at final approach speed. There's a tailwind. My ND shows RED terrain all quadrants. So now I ask myself these questions. Can I “S” turn or 360...Hell NO! Shall I Go-Around and take a chance flying one of these widow-maker missed approaches...It depends. OR, can I perform a simple Forward Slip and be stable by 1000 ft AGL? Yes, I can. I would submit to you, given these circumstances, a Forward Slip can be a BETTER option than a Go-Around. Unless you want to give me a GREEN cockpit and a set of Night Vision Goggles, I think this maneuver is a good one to have in your "Bag of Tricks".
Don't get me wrong. I prefer a straight in same as anybody else. But I don't wish to debate the merits of a maneuver that has served me well, 5 or 6 times over the course of my career. It’s safe, it’s approved by the FAA, and it works. When someone tells me it’s unsafe, I get pissed cause I think it can save your @$$. One of the things I learned early on is " The PK (probability of kill) of a mountain is 100%”. Now, if you don't think you have the skills to do one, then don't. However, if you can’t do one of these, I don’t think your chances are much better on a “Window-Maker”. Put it this way…a simple Forward Slip is better than the potential CLUSTER FOOK waiting for you in the dark. And I’ll damn-well do again if I have too.
Notch Johnson here. I've been away the past few days, with my girl BJ, slipping her other things besides airplanes. She likes to slip out to the country and ride the baloney pony with me. Anyways, I'm back and I'm truly astounded at the response of this thread. Though I think it has more to do with my charming personality than anything else. Right? I didn't want to discuss the merits of a simple flight maneuver, but you are right...I don't own this thread. So forgive me. Ok then.
Here's an excellent question on reader’s minds, submitted by Mouse...
"For the benefit of my curiosity when would you envisage needing this particular 'trick'?"
Well readers here my short response….”When going around is not the BEST option”.
I can hear you all now...."GASP! Oh the Horror! Murmur! Are you mad, man! Going around is ALWAYS the best option!" I’m my opinion; this is not always the case. Let me explain. It seems to me, many of you may only be familiar with flying into “flat and rolly" places like LHR. You can be forgiven for holding the view that Going Around is always superior to slipping it in. However, let me take you into some of the "Salad Bowls of Terrain" in places like Central/South America and the Caribbean. These places are scary enough in the daytime; try a visit at night. Many of these places have some of the most complicated and insane "Missed Approach" procedures you could imagine. Their "Engine-Out Missed Approach" procedures are even worse! You look at them and you say ..."You've got to be joking me! Right!" It looks like they were developed to satisfy some legal requirement knowing full well that Chuck Yeager might not be able to pull it off.
Anyways, case in point. I'm flying into one of these "Salad Bowls". I see that I'm high by a couple of thousand feet. I'm fully configured at final approach speed. There's a tailwind. My ND shows RED terrain all quadrants. So now I ask myself these questions. Can I “S” turn or 360...Hell NO! Shall I Go-Around and take a chance flying one of these widow-maker missed approaches...It depends. OR, can I perform a simple Forward Slip and be stable by 1000 ft AGL? Yes, I can. I would submit to you, given these circumstances, a Forward Slip can be a BETTER option than a Go-Around. Unless you want to give me a GREEN cockpit and a set of Night Vision Goggles, I think this maneuver is a good one to have in your "Bag of Tricks".
Don't get me wrong. I prefer a straight in same as anybody else. But I don't wish to debate the merits of a maneuver that has served me well, 5 or 6 times over the course of my career. It’s safe, it’s approved by the FAA, and it works. When someone tells me it’s unsafe, I get pissed cause I think it can save your @$$. One of the things I learned early on is " The PK (probability of kill) of a mountain is 100%”. Now, if you don't think you have the skills to do one, then don't. However, if you can’t do one of these, I don’t think your chances are much better on a “Window-Maker”. Put it this way…a simple Forward Slip is better than the potential CLUSTER FOOK waiting for you in the dark. And I’ll damn-well do again if I have too.
If you are "a couple of thousand feet high" then making the missed approach gradient would be a doddle, even with high terrain in the area - unless you began the approach at some massive overload.
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One assumes dvt that your company forgot to tick the "speedbrake" option when ordering their Boeings?
(Anyone else flummoxed by the "baloney pony" remark, or is he just being crude?)
(Anyone else flummoxed by the "baloney pony" remark, or is he just being crude?)
Bally Heck,
Are you quoting from a Boeing Manual, or a company version of a Boeing manual, that could be the difference, unless Boeing has changed things since I last operated B767.
As I said before, those numbers are very B744.
To those who were brought up on wings level/crab cross wind approaches, the B767 came as quite a shock to some, as if Boeing had committed some kind of heresy. As the manual will tell you elsewhere, you almost can't scrape a pod on B767, short of "shortening" a main gear, you will ding the nose or tail cone and a wing tip before you get a pod, quite a change from the "good old" 707.
Where I was working, very strong cross winds in severe clear conditions were common, there was no mistaking the behavior of the aeroplane.
Tootle pip !!
Are you quoting from a Boeing Manual, or a company version of a Boeing manual, that could be the difference, unless Boeing has changed things since I last operated B767.
As I said before, those numbers are very B744.
To those who were brought up on wings level/crab cross wind approaches, the B767 came as quite a shock to some, as if Boeing had committed some kind of heresy. As the manual will tell you elsewhere, you almost can't scrape a pod on B767, short of "shortening" a main gear, you will ding the nose or tail cone and a wing tip before you get a pod, quite a change from the "good old" 707.
Where I was working, very strong cross winds in severe clear conditions were common, there was no mistaking the behavior of the aeroplane.
Tootle pip !!
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Too right LeadSled, roaring forties mate, can’t handle a stiff crosswind, better go home and cry oily tears on mamma’s cotton apron lap.
So, dvt, you wanna a medal friend? Of course you can slip a large aeroplane, x-wind land or descend, all works the same, doesn’t take an idiot savant to put it together. Point is, friend, set her down on the first third, fuselage aligned with the centerline, on speed, that’s a good enough landing.
Anybody gotta serious a problem with that?
So, dvt, you wanna a medal friend? Of course you can slip a large aeroplane, x-wind land or descend, all works the same, doesn’t take an idiot savant to put it together. Point is, friend, set her down on the first third, fuselage aligned with the centerline, on speed, that’s a good enough landing.
Anybody gotta serious a problem with that?
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BS, a hearty I'm with you on this one!
If I remember the original query on this subject it was can you do it? I don't know, as I have never flown a Boing product. I do fly a Saab, however. The Saab manual specifically recommends a wing down landing, which if I understand anything means a forward slip technique (or else an ealiy arrival at the terminal). Maybe the Boing manual has a similar paragraph?
On the subject of 'slips'(aeronautical): as far as I can work itout there is little to choose aerodynamically between the foreward and the side versions, but do any of you remember slipping and sliding turns (not enough rudder/too much rudder)? You are all going to lose your medicals to ulcers if you don't relax a little.
If I remember the original query on this subject it was can you do it? I don't know, as I have never flown a Boing product. I do fly a Saab, however. The Saab manual specifically recommends a wing down landing, which if I understand anything means a forward slip technique (or else an ealiy arrival at the terminal). Maybe the Boing manual has a similar paragraph?
On the subject of 'slips'(aeronautical): as far as I can work itout there is little to choose aerodynamically between the foreward and the side versions, but do any of you remember slipping and sliding turns (not enough rudder/too much rudder)? You are all going to lose your medicals to ulcers if you don't relax a little.
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And furthermore, tried it yesterday on an MD-11, no big deal. As far as I can tell, if you take into account airflow disruption to the downwind engine(s) and pitot/static ports by compensating with extra airspeed during the maneuver, it’s very benign stuff, my son’s kid sister could pull it off without wetting dvt’s drawers.
Can’t really believe the above garbage regarding fin sideloads (AA587 notwithstanding), surely the designers took into account the possibility of repeated heavy turbulence encounters and max-dem crosswind landings.
Also not really sure why Prof Davies aka Handling the Big Jets pens his cryptic warnings regarding this subject re large transport category airplanes. Anyone know if he’s still alive, willing, and able to provide a reasonable explanation? If not, surely the Cathay Old School Boys must know!? They know everything, bless their degenerate RAF hearts!!
Can’t really believe the above garbage regarding fin sideloads (AA587 notwithstanding), surely the designers took into account the possibility of repeated heavy turbulence encounters and max-dem crosswind landings.
Also not really sure why Prof Davies aka Handling the Big Jets pens his cryptic warnings regarding this subject re large transport category airplanes. Anyone know if he’s still alive, willing, and able to provide a reasonable explanation? If not, surely the Cathay Old School Boys must know!? They know everything, bless their degenerate RAF hearts!!
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Bug Smash -- I readily concede you may be right - that slipping larger aircraft for glide slope enhancement just doesn't matter as an airframe life-limiting issue, but ONE detail is a source of concern:
Tail strength, etc are related during design to anticipated max crosswind speed for a given aircraft. However, no clear principle limits forward slips to the max angle implied by max crosswind speed. When slipping 'for effect', one tends to want to crank it in hard to get the 'feel' and then back off somewhat for tuning the result.
Done some distance above ground and at the pilot's discretion, a controllable fwd slip could quite possibly present an angle to the relative wind of TWICE what the max crosswind landing will do. Furthermore, this will be happening at velocities well above touchdown speed.
So, given that aerodynamic loads often increase at the cube of the airstream (vector) velocity, in fairly normal slip speedbraking one might be looking at 4x the tail load of a max allowed crosswind manoeuver - and that is before increments for turbulence and handling induced load factors.
Tail strength, etc are related during design to anticipated max crosswind speed for a given aircraft. However, no clear principle limits forward slips to the max angle implied by max crosswind speed. When slipping 'for effect', one tends to want to crank it in hard to get the 'feel' and then back off somewhat for tuning the result.
Done some distance above ground and at the pilot's discretion, a controllable fwd slip could quite possibly present an angle to the relative wind of TWICE what the max crosswind landing will do. Furthermore, this will be happening at velocities well above touchdown speed.
So, given that aerodynamic loads often increase at the cube of the airstream (vector) velocity, in fairly normal slip speedbraking one might be looking at 4x the tail load of a max allowed crosswind manoeuver - and that is before increments for turbulence and handling induced load factors.
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In answer to the topic in question.....
Yes, the B737-800 can be forward slipped to increase descent rate on final approach but in 5000 hours of flying this aircraft I have only seen it done once and I am hoping that I never see it again. It is extremely uncomfortable - and not just for the passengers.
To end up in a situation where it would be verified is extremely unlikely and would be the result of incompetence on behalf of not only the ATC at the time but also both flight crewmembers.
Orbits on final have their own dangers (see the A320 crash in Bahrain whereby the circuit was performed with neither height loss or speed loss) however are alot more comfortable for aircraft and crew.
I am sure that Boeing recommendation for forward slipping as a way of increasing descent rate on finals would be the same as their recommendation for using speedbrake with flaps more than 15 or maintaining flap limit speed when extending flaps (using flaps as speedbrakes)...... i.e. NOT.
Do it once if you don't believe me. After doing so I am sure you will not do it again if your airline wants to keep their passengers.
Yes, the B737-800 can be forward slipped to increase descent rate on final approach but in 5000 hours of flying this aircraft I have only seen it done once and I am hoping that I never see it again. It is extremely uncomfortable - and not just for the passengers.
To end up in a situation where it would be verified is extremely unlikely and would be the result of incompetence on behalf of not only the ATC at the time but also both flight crewmembers.
Orbits on final have their own dangers (see the A320 crash in Bahrain whereby the circuit was performed with neither height loss or speed loss) however are alot more comfortable for aircraft and crew.
I am sure that Boeing recommendation for forward slipping as a way of increasing descent rate on finals would be the same as their recommendation for using speedbrake with flaps more than 15 or maintaining flap limit speed when extending flaps (using flaps as speedbrakes)...... i.e. NOT.
Do it once if you don't believe me. After doing so I am sure you will not do it again if your airline wants to keep their passengers.
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Point taken arcniz. Surely, however, the designers must take into account the possibility of a heavy turbulence encounter at high speed (something that would potentially generate stresses far higher than a max x-wind landing), violent yaw-damp failure induced dutch roll, or engine-out maneuvering at high power settings when considering maximum lateral loads to be withstood by the fin assembly.
redturk, I agree, the maneuver is not a pretty one, but for the purposes of understanding large aircraft behaviour and design limits, a very interesting one.
redturk, I agree, the maneuver is not a pretty one, but for the purposes of understanding large aircraft behaviour and design limits, a very interesting one.
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bugg smasher,
One ought to be VERY circumspect in presuming just what the design team does and does not consider.
The design standards, as frozen for the particular design, determine the minimum set of requirements for which compliance must be shown.
There are many areas where additional work would be very nice to have ..... whether the design group addresses such matters is difficult to determine. Having been involved in such things, I can only say that one ought to be a little cautious on the line ......
This is one of the reasons that we ought to operate, to the maximum extent reasonably practicable, in sensibly strict compatibility with the manufacturer's AFM and crew manual data.
It may be a bit too late, at the time, to discover that you have pushed the boundaries a little too far ...........
One ought to be VERY circumspect in presuming just what the design team does and does not consider.
The design standards, as frozen for the particular design, determine the minimum set of requirements for which compliance must be shown.
There are many areas where additional work would be very nice to have ..... whether the design group addresses such matters is difficult to determine. Having been involved in such things, I can only say that one ought to be a little cautious on the line ......
This is one of the reasons that we ought to operate, to the maximum extent reasonably practicable, in sensibly strict compatibility with the manufacturer's AFM and crew manual data.
It may be a bit too late, at the time, to discover that you have pushed the boundaries a little too far ...........
Last edited by john_tullamarine; 6th Aug 2002 at 00:51.
LeadSled
It's odd how the memory plays tricks on one - I would also have said, from memory, that the L1011 had a higher x-wind limit. Just dug out the Big Airways/Callie F.M. and the only reference to x-wind limits appears in the A/P engaged to 50' RH limits, which gives "reported wind not greater than 26kts, x-wind component not greater than 20 kts, tailwind not greater than 10 kts and no abnormal turbulence". For Tristar x-wind operation the forward slip was, of course, the ONLY way to do it and the other relevant entry in the F.M. is in the section on x-wind landings ...
"Touchdown on one main landing gear is permissible and recommended"
It's odd how the memory plays tricks on one - I would also have said, from memory, that the L1011 had a higher x-wind limit. Just dug out the Big Airways/Callie F.M. and the only reference to x-wind limits appears in the A/P engaged to 50' RH limits, which gives "reported wind not greater than 26kts, x-wind component not greater than 20 kts, tailwind not greater than 10 kts and no abnormal turbulence". For Tristar x-wind operation the forward slip was, of course, the ONLY way to do it and the other relevant entry in the F.M. is in the section on x-wind landings ...
"Touchdown on one main landing gear is permissible and recommended"
quidquid excusatio prandium pro
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j_t, if you were involved in aircraft design, perhaps you might be able to dig a bit and provide us with more information on fin design requirements. In addition to the above examples, I have been stuck on the ground in typhoon conditions in the Far East, and have seen from my hotel room window 747’s parked directly across the path of the oncoming storm. Those fins were subject to a sustained broadside (several hours) of 100 knots or more, with frequent gusts to 150, yet to my knowledge, those aircraft were not subject to any special inspection procedures afterwards. The only conclusion I can draw from this is that brick shathoose strength (technically speaking) is a basic design requirement for that particular aircraft structure.
Perhaps you can enlighten us with the facts.
Perhaps you can enlighten us with the facts.