Mr.BA From Singapore, joined Sep 2000, 3423 posts, RR: 23 Posted (10 years 7 months 1 week 5 days 6 hours ago) and read 3557 times:
Hi guys,
I apologise for bringing this up again. I do recall about someone starting a thread on this but I can't find it after some searching.
Anyway, would really like to know how did this pilot managed to straighten out after touching down at such an angle? Given it's speed it would have ran straight into the habour? Photographer Colin said it slid sideways on the runway but how is this possible? The runway is not kilometres wide, how did he actually bring the plane back to the left so much even at full aileron and rudder?
Finally would like to ask B747 drivers how sensitive is the B747 in maneuvering? Say in crosswind landings, sudden changes in wind direction or speed will result in the plane yawing or 'rolling', is it possible t make sudden and small changes in pitch and roll to stay on track? On landing roll, say crosswind is at 30 knots, does the plane really slide off the centre line if ailerons are not put into the wind and rudder at the opposite?
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 1, posted (10 years 7 months 1 week 5 days 4 hours ago) and read 3499 times:
Alvin,
as for rudder authority: When the mains (well aft of the CoG) are dragged sideways across the runway it is bound to create quite a yaw moment to help the rudder get the aircraft straightened out...
Still wouldn't want to be onboard though.
Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 4, posted (10 years 7 months 1 week 5 days ago) and read 3426 times:
Saintsman,
reverse thrust takes a moment to kick in. Until the engines have spooled up from their touchdown RPM, the reversers really only cancel out (at least part of) the residual idle thrust of the engines. I don't know how fast the reversers would kick in on whatever engines are on that 747, and I don't think it would help much. Besides, I really hope the pilot in the above situation had both hands on the yoke and wasn't fiddling about with the power levers!
Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
B747skipper From , joined Dec 1969, posts, RR: Reply 5, posted (10 years 7 months 1 week 4 days 11 hours ago) and read 3304 times:
Hello Alvin -
xxx
The "size" of the aircraft, whether a 747 or a J3C Cub does not really matter, in a sense that all is in proportion - i.e. size of flight controls, power of the engines... I do not see anything spectacular about these pictures of that landing aircraft...
xxx
Granted that it is advisable to be "stabilized" some 500 ft AGL for any given approach, but here we see a visual landing by a pilot probably quite familiar with his aircraft... and conditions were probably ideal as well.
xxx
For aircraft such as the 747, or the DC8 (particularly the 71/73 series), the limiting factor is "outboard engines" when banking aircraft in the nose high attitude, which brings these engines cowlings close to the ground. I would always recommend a flare and touchdown in "wings level attitude", even if it means some amount of crab into a crosswind.
(s) Skipper
Cx flyboy From Hong Kong, joined Dec 1999, 6341 posts, RR: 56 Reply 7, posted (10 years 7 months 1 week 4 days 1 hour ago) and read 3215 times:
I would say that landing was pretty spectacular!! I certainly don't want to do any like that!!
Look at his point of touchdown compared to the top of the Thai MD11 tail, then look at where he is in the next photo, and you can see how far he has slid sideways.
Boeing actually recommends landing on a wet runway in a crosswind like that. The crab angle will take itself out upon touchdown. On a dry runway however, land 45 degrees off the runway like that and you are bound to do serious damage to your tyres and possibly risk a pod strike, which happened in this case.
The rudder on the 747 is very large, and it would help to straighten out, but the majority of the straightening would have been done by the gear and just the way the aircraft is built. Nevertheless, you wouldn't want to do landings like that every day!!
Cx flyboy From Hong Kong, joined Dec 1999, 6341 posts, RR: 56 Reply 9, posted (10 years 7 months 1 week 3 days 23 hours ago) and read 3180 times:
Well, if you look at the windsock, there is only a slight crosswind from the right, which should not be a problem for any pilot. Kai Tak was difficult in the best of times and if you did not get it right, you could find yourself still trying to get onto centerline way past the threshold. This NCA appears to have done this, and going from being relatively lined up to being way off the runway heading in such a short time he probably used rudder to align himself to the runway....with the results shown here.
Mr.BA From Singapore, joined Sep 2000, 3423 posts, RR: 23 Reply 10, posted (10 years 7 months 1 week 3 days 23 hours ago) and read 3167 times:
Pardon me for asking this. I've never seen any pilots imput rudder to align the plane with the runway, it's always ailerons that do the job. Any idea why it is not recommended to use rudder to center yourself or point yourself straight at the runway before touchdown?
FredT From United Kingdom, joined Feb 2002, 2184 posts, RR: 26 Reply 11, posted (10 years 7 months 1 week 3 days 22 hours ago) and read 3160 times:
Mr.BA,
you can handle a crosswind in two ways. One is to fly in aligned with the runway, holding the upwind wing low to slip into the wind and remain on the runway centerline. The other is to point the nose of the aircraft into the wind to compensate for the crosswind. The former is common practise in GA but less used on airliners for a number of reasons:
- Pax don't like slips. Slips spill their drinks and are less than comfortable. Especially in the rear end of the cabin, you can feel it when the pilot has restless feet and is playing with the rudder. And, however much you'd like to make those obnoxious people in the back thoroughly airsick, they pay for the flight so you have to treat them nicely.
- Swept wings and slips really don't mix too well. The upwind wing will have a larger perpendicular airspeed component than the downwind wing. As this component is the one which accounts for the lift, it creates a roll moment that you can live without.
- You have to level the wings prior to touchdown. If you don't you might have a podstrike if you're flying something with podded engines.
If you crab in, your wings are level but your aircraft and landing gear aren't aligned with the runway. Thus, you use rudder to take out the crab prior to touchdown. As you do, you might have to compensate with aileron to keep the wings level or there might be a pod strike.
Cheers,
Fred
I thought I was doing good trying to avoid those airport hotels... and look at me now.
Il75 From Argentina, joined May 2001, 260 posts, RR: 0 Reply 12, posted (10 years 7 months 1 week 3 days 21 hours ago) and read 3118 times:
I was long amazed by those pictures and certainly said to myself "lucky you you weren't at that plane". But then one day I saw a short film showing just this very same landing or another just identical.
It was for me a great example of the differences between still and motion picture. You see the photographs and think "How is this going to end?" fearing it is impossible to straighten up the airplane. But the film is no dramatic at all. Yes, the nose of the plane was certainly pointing in a wrong direction -- for a second -- but immediately after landing the aircraft was rolling nicely in the middle of the runway. I even wondered if the passengers did notice anything at all.
A shame I do not remember the site where I found the film but I think it was something under the name "spectacular landings".
Mr.BA From Singapore, joined Sep 2000, 3423 posts, RR: 23 Reply 13, posted (10 years 7 months 1 week 3 days 14 hours ago) and read 3048 times:
Hi Fred,
Thanks a lot for the reply! I've got a clear picture now.
Erico,
I'm sure if that's a passenger jet the passenger will definately feel something. Even a slight kick in a rudder to center your nose on the runway by the pilot you will feel it in the cabin. I realy don't know how wuld this feel.. I guess everyone would be foreced to the right.
B747skipper From , joined Dec 1969, posts, RR: Reply 14, posted (10 years 7 months 1 week 3 days 12 hours ago) and read 3024 times:
Just think about a long fuselage airplane - merely for taxying - and you swing the tail around to make a 90 degree turn to line up on the runway... If you dont do it slowly and smoothly, you might get a couple of flight attendants falling on their face while they try to run to their stations...
xxx
Like I said here before many times, learning to taxi a 747 is the only difficult thing... you need to have the "mind" of an 18 wheel driver (think how they manage their turns on streets) - same for us, the nose wheel is AFT of the pilot seats - and "where is the main gear"... then the "yaw movement" of the tail on the ground - sideloads, somebody mentioned passengers not liking it, true... The same thing applies to all long fuselage airplanes, MD11s, even the long DC8s.
xxx
Think of it - we got 18 wheels as well
xxx
(s) Skipper
B747skipper From , joined Dec 1969, posts, RR: Reply 16, posted (10 years 7 months 1 week 3 days 4 hours ago) and read 2970 times:
Mr.BA that is correct, the longer the plane, the worse it is...
And for the other facts (directional control) realize that at high speed - all is done by the rudder, a nose wheel is about as effective as a piece of wet paper tissues... In the 747 the rudder starts to be effective as early as about 60-70 kts, the nose wheel is just good for taxi speeds and "initial line up" for takeoff. Nose wheel would be totally unable to counter the yaw moment of an outboard engine at high power, the opposite at idle...
xxx
I once saw a 747 almost making a ground loop because of uneven engine power application, and I could see the pilot attempting to use the nose wheel steering, the plane ended up some 45 to 60 degrees sideways on the runway. These passengers probably were not too happy.
xxx
(s) Skipper
B747skipper From , joined Dec 1969, posts, RR: Reply 18, posted (10 years 7 months 1 week 2 days 18 hours ago) and read 2902 times:
Mr.BA -
xxx
We taxi at 20 kts (max) and make "normal turns" at 10 kts... tight turns probably around 5 kts, almost standing still... (speed is read from INS)...
xxx
The airplane, so slow in tight turns needs a little bit of "engine power" on the outboard engines, for me "a knob worth of power" to assist the aircraft to continue turning and moving... so yes we use differential power, but as far as the brakes, nobody uses differential braking at all for turns...
xxx
Brakes and wheel can overheat very easy on a 747 taxiing for takeoff, we have brake temperature gages. If you see an aircraft taking off and not retracting the gear for a couple of minutes, maybe it is because they are cooling the brakes as a precaution...
xxx
Happy contrails -
(s) Skipper
Klaus From Germany, joined Jul 2001, 20860 posts, RR: 55 Reply 19, posted (10 years 7 months 1 week 2 days 13 hours ago) and read 2888 times:
I was wondering (and had asked a few months before, but can´t remember it answered): Does the 747 body gear steering play any part in crabbed landings or does the steering stay locked all the time unless taxiing?
I can imagine quite a few reasons for not using it in landings, but I don´t know for sure.
(I just watched the movie of the KAL 747 Kai Tak landing again; It looks like a 45 degree swing within about three seconds right before touchdown. Even with the perspective probably exaggerating, I can´t imagine that nobody felt anything, especially in the back rows...)
B747skipper From , joined Dec 1969, posts, RR: Reply 21, posted (10 years 7 months 1 week 2 days 12 hours ago) and read 2872 times:
Dear Klaus -
Regarding your question about the body gear steering in the 747, the "switch" is ON, for taxi, we arm the switch to turn off the runway at completion of the landing. It stays ON, until we line-up on the takeoff runway for departure, and placed OFF before we start moving the power for takeoff... one of the last thing on our before takeoff check-list...
xxx
The takeoff warning horn in the 747 includes the standard "Boeing items" which are - flaps (TE-LE) not in takeoff position, trim not in the green band, speed brakes handle not down/locked AND BODY GEAR NOT CENTERED/disarmed... the warning horn would sound...
xxx
For our future 747 pilots here - you will learn that to taxi on icy taxiways, it is better to leave the body gear system OFF (centered gear) to decrease the danger of skidding on ice...
xxx
Staffan, I dont know if it is "45 degrees", but that main landing gear can take a lot of sideloads - no figures to give you, sorry...
xxx
(s) Skipper
Mr.BA From Singapore, joined Sep 2000, 3423 posts, RR: 23 Reply 22, posted (10 years 7 months 1 week 2 days 10 hours ago) and read 2850 times:
Thanks Skipper for the explanation.
Just came to mind, is it better to taxi with flaps up for as long as possible when there are snow/standing water and areas prone to icing? I can imagine flaps and every part of the wing are very important. Are the flaps very prone to have ice formed on it? Also, in very cold conditions, how do you warm the fuel and hydraulic liquids up (I think the minimum fuel temperature for start is the same as the 744 on the classics?)? Would turning the nose gear help?
B747skipper From , joined Dec 1969, posts, RR: Reply 23, posted (10 years 7 months 1 week 2 days 9 hours ago) and read 2847 times:
Dear Mr.BA -
xxx
There is a minimum fuel temperature - Jet A-1 we can go to -37 Celsius, but we must heat fuel (in the JT9D engines) for 1 minute before takeoff if the temperature is between +5 C to -15 C... and 2 minutes of less that - 15 C...
We can read temperature of fuel in main tank #1, as well as fuel going to each engine... A trick: fuel temperature of fuel in center wing tank is always warmer... I always keep some there for the end of cruise, so if fuel is very cold, that fuel can be used if necessary - flight engineers taught me that...
xxx
The CF6 engine does not require fuel heat (no fuel heat switches on 747s with CF6)... The RR engines have fuel heat switches, never flew these...
xxx
Hydraulics, well, no minimum temperature... and we have 4 separate systems in the 747, so warming up one (i.e. moving nose wheel steering) would have no effect on the 3 other hydraulic systems... hydraulics gets warm fairly fast, the worry is to "cool hydraulics" rather than heating the Skydrol...
Hydraulic fluid is cooled by heat exchangers (radiators) submerged in the fuel tanks... cools off hydraulics, warms up the fuel in the tanks...
xxx
With ice and snow, we taxi flaps up, to prevent ice and snow from entering into the spacing into which they are to retract after takeoff... then when we position on the runway, we extend the flaps as required, then we have to complete the check list we could not do (since the flaps were not extended). That is the reason why, with ice and snow, your airplane might delay the takeoff about 1 minute on the runway, it is for completion of check lists...
xxx
Finally, after flaps retraction on takeoff, we might "cycle the gear down for a few seconds" to clean off any ice or snow that might be on it, as it could freeze some gear components or micro switches inside the wheel well... so if that happens while you departed, you know why now...
xxx
With ice and snow, finally, after landing, we do not retract flaps, as there may be ice and snow inside the retraction space... maintenance would check first to perform retraction clear of any ice...
xxx
That's it...
(s) Skipper
Klaus From Germany, joined Jul 2001, 20860 posts, RR: 55 Reply 24, posted (10 years 7 months 1 week 2 days 5 hours ago) and read 2832 times:
Thanks!
25 Mr.BA: Hello Skipper, Thanks again for such an informative post. Hope it's not taking up to much of your time! By the way, I've read on landing rolls reverse
26 L-188: I am going to chime in a bit on flaps and taxing on ice. On the 727's that I used to turn on occasion when the plane would land on a slushy runway (ve
27 Mr.BA: Hello L-188, Interesting stories there, thanks so much for sharing it. Talking about brakes freezing up, in modern aircraft are there systems to make
28 L-188: They then got a couple of sunflower and loaders to bury the 747 This is why you shouldn't trust the spellchecker I don't think there are any systems t
29 B747skipper: Dear L-188 - xxx Please verify the story of the "JAL cargo with cows, buried, etc." - I am so impressed by the the fact that you saw the pictures befo
30 B747skipper: For reversers - Hello Mr.BA - xxx Note that in case of emergency, full power reverse may be used until the aircraft is stopped... Engines may not like
31 Cx flyboy: We normally land with reserve idle in Cathay. We crack the reversers to have them at the ready incase we need them, however, we don't usually use any
32 L-188: You realize that you just called my uncle a liar there Skipper.
33 B747skipper: L-188, please verify, JA8122, 747-246B passenger a/c, ANC on 16 DEC 1975... Then tell me that your uncle did not remember, after all, that is long ago
34 B747skipper: L-188 - xxx Just did research that accident with NTSB through AirDisaster.com... Here is the reference for you to check... www.airdisaster.com/cgi-bin
35 Mr.BA: Hello Skipper and Cx flyboy, Thanks a lot for the explanations and information. For CX, does it mean idle reversers are always used as much as possibl
36 B747skipper: Hola Alvin - xxx With the old Classics, when landing on wet runways, autobrakes go to MED... Only MIN, MED and MAX on autobrakes rate selector for the
37 Cx flyboy: Alvin, We use more than idle reverse when we feel it should be a good idea. On a long dry runway, we use idle only. If it was wet, I would use full re
38 Mr.BA: Hello Cx flyboy and Skipper, Thanks a lot again. Always interesting to learn more, hope you guys didn't mind, sorry to have dragged this so long and h
39 B747skipper: Alvin - Did you get that book I recommended to you about the 747...? (s) Skipper
40 Mr.BA: Hi Skipper, Can't find it anywhere till now. Even Amazon don't give a clue. Cheers!
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