MerlinIIIB From Norway, joined Aug 2005, 120 posts, RR: 0 Posted (7 years 2 months 3 weeks 3 days 3 hours ago) and read 4019 times:
Last night a MyTravel A321 slid sideways on the runway at Torp (Norway) stopping at the very end of the runway. It was a 3 cm layer of wet snow on the runway. The aircraft heading was approx. 30 degrees offset from the runway heading when it stopped.
According to local media reports, the "sideways slide" enhanced the retardation preventing the aircraft from leaving the paved part of the runway.
To you pilots - can deliberate pilot actions create a sideways slide, as a last resource to enhance breaking? (asymmetric reverse thrust...)
Jamesbuk From United Kingdom, joined May 2005, 3968 posts, RR: 5 Reply 1, posted (7 years 2 months 3 weeks 3 days 3 hours ago) and read 3993 times:
You can slow an aircraft down by turning it on the runway because then all the slowing power isnt on the bearings of the wheel but then on the side of the wheel, much like dragging a rubber across a desk, on the smaller edge its easier but on the longer edge its harder.
If there is a panic to slow down normally a pilot would swurve the aircraft, e.g to the left go about 15- 30 degrees off course then swing it round the other way, this is very effective but can damage the aircraft.
Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 3, posted (7 years 2 months 3 weeks 2 days 22 hours ago) and read 3880 times:
In GA aircraft, landing gear don't handle side loads well...I'd hate to try it on purpose in an airliner!
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
MerlinIIIB From Norway, joined Aug 2005, 120 posts, RR: 0 Reply 4, posted (7 years 2 months 3 weeks 2 days 15 hours ago) and read 3798 times:
Quoting Jamesbuk (Reply 1): a pilot would swurve the aircraft, e.g to the left go about 15- 30 degrees
Thanks. According to the authorities here in Norway, the pilot did indeed slide the aircraft as a last resource to stop it. The parking break was on during the last 300 metres of the slide maneuver. AC was not damaged, a wheel was replaced.
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 6, posted (7 years 2 months 3 weeks 2 days 3 hours ago) and read 3666 times:
Well, I guess actual pilots no longer read this forum. I've been waiting for one of them to address this:
Quoting Jamesbuk (Reply 1): You can slow an aircraft down by turning it on the runway because then all the slowing power isnt on the bearings of the wheel but then on the side of the wheel, much like dragging a rubber across a desk, on the smaller edge its easier but on the longer edge its harder.
If there is a panic to slow down normally a pilot would swurve the aircraft, e.g to the left go about 15- 30 degrees off course then swing it round the other way, this is very effective but can damage the aircraft.
Terrible! This is bad info!
If your flight instructor tells you something like this, report him and change instructors.
Nowhere in the world that I've ever heard of is this a recommended procedure.
There might be slightly more drag on the contact patch of a tire-on-pavement when it is stationary then you try to slide it sideways, but if a tire on a car or an airplane is moving with a sidways vector it has broken loose from the pavement and is skidding. The most effective braking effort is always straight ahead with the direction of travel perfectly aligned with the plane of rotation with anti-skid braking rapidly gripping and releasing the brakes.
In addition, airliner landing gear don't like sideloads any more than light plane landing gear does.
Not having been there I cannot say what happened in the thread-starter incident but I've seen similar things and it was always due to a partial loss of control - which is never a good element of procedure.
Once in a Cessna 206 I landed on a packed-snow runway and when we slowed down the plane just drifted around and went sideways and slid that way until it ran out of kinetic energy - fortunately before it ran out of runway.
I've seen a 707 get into reverted rubber hydroplaning after landing with a tailwind and slide the full length of a very long runway. The skid was more than ten thousand feet! It came to a stop about 15-20 degrees off runway heading with its radome just about ten feet from the blast fence. Because of the angle they were then able to run up number four and make the turn back to the runway/taxiway exit. They did not turn sideways to slow it down!
My guess, having flown the A-321 and having landed on hundreds if not thousands of slick, icy or contaminated runways is that they just sort of lost it at the end. Moving sideways in an airliner is just likely to hasten your departure from the runway without regard to the location of the taxiways, parked aircraft or service vehicles.
Happiness is not seeing another trite Ste. Maarten photo all week long.
2H4 From United States of America, joined Oct 2004, 8950 posts, RR: 62 Reply 7, posted (7 years 2 months 3 weeks 2 days 2 hours ago) and read 3653 times:
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 8, posted (7 years 2 months 3 weeks 2 days 2 hours ago) and read 3645 times:
Not really "back" exactly. I just could not let that statement stand unchallenged. Should not have to jump in to comment on technical info or advice offered by student pilots, non-pilots or FS pilots but there you are . . .
"Just when I think I'm out they drag me back in." - Michael Corleone
Been doing other things. I might occasionally jump on something like this.
regards
Slam
[Edited 2006-03-28 20:13:31]
Happiness is not seeing another trite Ste. Maarten photo all week long.
KELPkid From United States of America, joined Nov 2005, 5962 posts, RR: 4 Reply 9, posted (7 years 2 months 3 weeks 2 days 2 hours ago) and read 3636 times:
Quoting SlamClick (Reply 6): Well, I guess actual pilots no longer read this forum. I've been waiting for one of them to address this
See reply 3. I attempted to raise a based on my experience, but I guess I was just being too subtle...and if I start going down the runway sideways, I'd seriously be thinking about the NTSB or NASA report I'd have to file...as well as concentrating on how to get back on the centerline and under control
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
David L From United Kingdom, joined May 1999, 9242 posts, RR: 42 Reply 10, posted (7 years 2 months 3 weeks 2 days 2 hours ago) and read 3630 times:
Quoting 2H4 (Reply 7): It's great to have you back, SlamClick!
Indeed!
Quoting SlamClick (Reply 6): if a tire on a car or an airplane is moving with a sidways vector it has broken loose from the pavement and is skidding.
Exactly. Aircraft aside, I think I'd rather take my chances with a slower, head-on car crash than a faster, side-on crash. Needless to say, I've never heard anyone else recommend handbrake turns for the average Joe.
Quoting SlamClick (Reply 6): I guess actual pilots no longer read this forum.
There are still a few but the poor sods have to drag themsleves off flying from time to time so they tend to miss some topics. They have my sympathy .
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 11, posted (7 years 2 months 3 weeks 2 days 2 hours ago) and read 3630 times:
Quoting KELPkid (Reply 9): I guess I was just being too subtle
Yeah, I did see your post. I guess I was hoping for something a little more emphatic.
I ration my subtlety among people whom I must deal with face to face. (and might be able to whup me)
Happiness is not seeing another trite Ste. Maarten photo all week long.
Wingscrubber From UK - England, joined Sep 2001, 835 posts, RR: 0 Reply 12, posted (7 years 2 months 3 weeks 2 days 2 hours ago) and read 3618 times:
I'd like to probe this a little deeper if I may; hypothetically can a pilot abort the landing, rotate and go around if he finds he is unable to stop on a very slick runway after touchdown?(Assuming no slide!) If so, at what point is he commited to stopping? I know a touch-n-go is no biggy in a small Cessna, but what about in aircraft like the A320 aforementioned?
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 13, posted (7 years 2 months 3 weeks 2 days 1 hour ago) and read 3603 times:
Quoting Wingscrubber (Reply 12): what about in aicraft like the A320 aforementioned?
Yes we can, and occasionally do abort a landing after touchdown, though the suitability of the runway as regards condition and stopping action should have been decided before the approach was commenced.
Picture it like this. A plane is taking off; it goes from a standing start, ever faster until it has flying speed and it clears all obstructions with the required margin. At any given point along the runway there is a corresponding speed one might expect during that acceleration.
Another plane is landing; it crosses the fence on the profile, on speed, touched down and applies braking eventually coming to a stop.
At some point along the runway the landing plane would be at the same speed as the taking-off plane was at that same point. After that the lander can no longer reject the landing. Before that point you can reject the landing and have more speed (more energy) than a plane taking off had at that point. (plus or minus response time, spoolup time etc.)
(We could also assume that a landing plane weighs less than a taking-off plane but I'll leave that alone.)
Problem is, it might not be easy to judge that crossover point along the runway. So I'd say, based on experience that if I'd touched down, gotten spoiler deployment, reverse thrust and have done some braking, I am probably going to stay on the ground and do whatever avoidance maneuver in two dimensions only.
That said, I have had a couple of occasions when I sure wished I'd done something different a couple miles back.
Happiness is not seeing another trite Ste. Maarten photo all week long.
Vikkyvik From United States of America, joined Jul 2003, 8313 posts, RR: 28 Reply 14, posted (7 years 2 months 3 weeks 2 days 1 hour ago) and read 3603 times:
Damn, there's a username I thought we'd never see again! Gladly, I was mistaken.
Quoting MerlinIIIB (Reply 4): Thanks. According to the authorities here in Norway, the pilot did indeed slide the aircraft as a last resource to stop it. The parking break was on during the last 300 metres of the slide maneuver. AC was not damaged, a wheel was replaced.
Do you happen to have a link to a report or article (preferably in English )? I'd be interested to read their reasoning.
~Vik
"Two and a Half Men" was filmed in front of a live ostrich.
I stand corrected!!
I based that statement on a episode of Air crash investigation, cant remember which one, but then i guess i should learn not to trust silly programmes like that!!
Rgds --James--
You cant have your cake and eat it... What the hells the point in having it then!!!
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 16, posted (7 years 2 months 3 weeks 2 days 1 hour ago) and read 3566 times:
Quoting Vikkyvik (Reply 14): I'd be interested to read their reasoning.
~Vik
I would too since there is only a rounded-metal inch or so keeping the tire on the rim. It is not that difficult to break the bead and roll one off the rim in sideload. I still can't see any advantage to a procedure that works against the brilliantly-engineered brakes.
Happiness is not seeing another trite Ste. Maarten photo all week long.
MerlinIIIB From Norway, joined Aug 2005, 120 posts, RR: 0 Reply 17, posted (7 years 2 months 3 weeks 2 days ago) and read 3554 times:
Quoting Vikkyvik (Reply 14): Quoting MerlinIIIB (Reply 4):
Thanks. According to the authorities here in Norway, the pilot did indeed slide the aircraft as a last resource to stop it.
Do you happen to have a link to a report or article (preferably in English )? I'd be interested to read their reasoning.
The Norwegian newspaper VG, Monday March 27 page 7 did interview the capt. involved in the March 26. incident at Sandefjord Airport Torp (TRF). My translation: "We did whatever we could to stop, during the last 300 metres parking breaks were engaged, said Capt. NN...(newspaper then add to this quote ...) Cpt. NN turned the aircraft into a sideways slide until it stopped at the very end of the runway". On local TV (TV Vestfold county) that same day, an AIBN (Accident Investigation Board of Norway) representative summarised pilot actions in a way which made me believe the newspaper description was accurate.
Is applying parking breaks normal in this kind of situation, no anti-skid?
Runway length at Torp is 2990 m, the A321 landed with some tailwind and on 3 cm layer of fresh wet snow. It was no daylight. Friction was measured 17 minutes prior to the landing, big debate in press about the reliability of such measurements.
Thanks to SlamClick for excellent replies (as usual).
TheSorcerer From United Kingdom, joined Oct 2005, 1047 posts, RR: 0 Reply 18, posted (7 years 2 months 3 weeks 1 day 23 hours ago) and read 3514 times:
Maybe they mean emergency brakes?
There are emergency brakes on the A321 aren't there?
thanks in advance
Dominic
ALITALIA,All Landings In Torino, All Luggage In Athens ;)
Vikkyvik From United States of America, joined Jul 2003, 8313 posts, RR: 28 Reply 19, posted (7 years 2 months 3 weeks 1 day 23 hours ago) and read 3511 times:
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Quoting MerlinIIIB (Reply 17): Is applying parking breaks normal in this kind of situation, no anti-skid?
I'm no pilot, but that sounds like a recipe for skidding right off of the end of the runway. I mean, in my car, on slippery ground, I wouldn't use the E-brake. I'd let the antilock system do its job. Anything to keep from locking the wheels, which I'd assume would translate to stopping aircraft as well.
Like always, correct me if I'm wrong, but it sounds like they got lucky.
P.S. MerlinIIIB, thanks for the translation.
~Vik
"Two and a Half Men" was filmed in front of a live ostrich.
Aogdesk From United States of America, joined Jun 2004, 933 posts, RR: 4 Reply 20, posted (7 years 2 months 3 weeks 1 day 23 hours ago) and read 3497 times:
Quoting TheSorcerer (Reply 18): There are emergency brakes on the A321 aren't there?
Aircraft have emergency or reserve braking systems, but in all of the cases of airframes that I'm familiar with, the secondary braking system relies on a separate SOURCE of pressure to be applied to the wheel/tire assy. For example, if system 'a' hydraulic pressure fails, which under normal conditions supplies pressure to the brakes, a reserve system could be selected to port system 'b' pressure to the brakes. On some airframes, the source of pressure is accumulated air, while in others its hydraulics from a completely separate system.
As far as the debate over intentionally skidding an aircraft, that sounds like it was made up by the media. What a great way to completely lose control, as you take the anti-skid right out of the picture, and also a great way to damage the landing gear with a serious sideload.
Okie From United States of America, joined Jul 2003, 2410 posts, RR: 3 Reply 21, posted (7 years 2 months 3 weeks 1 day 20 hours ago) and read 3443 times:
Well sliding a 321 at a 30 deg angle sideways 300 meters without rolling a tire off the bead, breaking a landing gear fuse pin, or having enough weight transfer to the leading wing to drag an engine or wing tip pretty much indicates a real slick runway
Not to throw anymore mud in the pie but I believe at some speed, 40kts comes to mind that the anti-skid shuts down. Now with limited traction the wheels may never have come back up to the threshold speed near the end of the landing run if the anti-skid turns its self off according to wheel speed.
If the plane uses KIAS to shut down the anti-skid then turning a plane 30 deg to the airflow will definitely effect the airflow to the pitot.
Maybe someone with a little better knowledge of the anti-skid will jump in here.
SlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 71 Reply 22, posted (7 years 2 months 3 weeks 1 day 20 hours ago) and read 3433 times:
I'm pretty sure the anti-skid uses wheel speed transducers as an input.
Pitot derived airspeed is pretty inaccurate below 70-100 knots or so. GPS/FMS derived groundspeed would be fairly accurate, would "know" both aircraft heading and actual direction/speed of travel. It would also have from the nav database, the runway being used and its heading, but again, I'm pretty sure it is wheel speed.
Don't want to mislead here. If I thought I might be headed for the weeds at the far end I would be using reverse thrust to the point of compressor stalls and I would be using maximum anti-skid braking. This means I'd be a stiff straight line from my shoulders on the seatback to my size-elevens on the brake pedals. After that I'd let the system work, or if it didn't work at least I'd done what I could.
At some point the locked-wheel protection might not be able to do its job, I don't know. But I would not back off the braking at this point and if that meant I slid a little sideways well, you do what you can.
I can picture me sitting there with the tiller at opposite lock, in a six-wheel drift, looking out over the copilot's nose at the approaching end of pavement!
I'm reminded of a friend who parked a DC-10 at Tehran many years ago. As soon as he set the parking brake the plane began to slide dead sideways across the ramp. He said "What a helpless feeling! What are you going to do? Put on the brakes?
Stories like these remind me of why I don't mind being retired.
Happiness is not seeing another trite Ste. Maarten photo all week long.
AJ From Australia, joined Nov 1999, 2376 posts, RR: 27 Reply 23, posted (7 years 2 months 3 weeks 1 day 20 hours ago) and read 3426 times:
We have been through a lot of training regarding contaminated runways since the overrun of a company 747-400 from a very wet runway.
I haven't flown an Airbus but Mr. Boeing is quite clear in the statement that once reverse thrust has been selected the landing must be completed. Aborting the landing with one reverser stuck open would be nasty to say the least!
Deliberately turning the aircraft on the runway would be very unwise as SlamClick has stated. If the aircraft is in reverse thrust changing the direction of the aircraft leads to a further loss of directional control (a component of the reverse thrust vector works against you). Again it's Mr. Boeing's direction that during a loss of directional control reverse is returned to idle until control is regained, completely against your natural reaction to halt the aircraft any way you can!
Fortunately the A321 and our 744 amongst others have been non-fatal providing a reminder of the dynamic environment in which we work.
Vikkyvik From United States of America, joined Jul 2003, 8313 posts, RR: 28 Reply 24, posted (7 years 2 months 3 weeks 1 day 19 hours ago) and read 3406 times:
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Quoting Okie (Reply 21): Not to throw anymore mud in the pie but I believe at some speed, 40kts comes to mind that the anti-skid shuts down.
What is the reasoning behind having the anti-skid system shut down at a certain speed? Wouldn't it be useful all the way to a stop (or at least, to, say, 10 kts)?
Thanks.
~Vik
"Two and a Half Men" was filmed in front of a live ostrich.
25 PurdueAv2003: The anti-skid should never "shut down". The system I'm most familiar with (737 Classic) uses input from rotary transducers at the wheels and air speed
26 Starlionblue: Same as in a car. Under a certain (low) speed anti-skid is shut down. Otherwise the wheels would never be allowed to stop. Eventually, they do have t
27 Vikkyvik: True, but I'm pretty sure this speed is pretty low on a car. I've felt the anti-lock brakes working at under 15 mph easily. Seems to me that technica
28 Zeke: It would be turned off as part of the loss of braking emergency recall. 3cm layer of snow, what were these guys trying to land on ? This year has see
29 David L: I can see the need for a reference speed to compare the wheel speed to otherwise the system wouldn't know when the wheels should be allowed to lock,
30 PurdueAv2003: The airspeed may not provide an accurate rate at lower speeds, but it does provide a quick and dirty method to indicate general forward movement on t
31 MerlinIIIB: I live 40 km from the airport, an at the time of the incident it was +0,5 C and light snow. Due to very low night temperatures, the ground was cold a
32 MarcoT: For airplanes I cannot meaningfully comment, while gut feeling is that 40 kts is too much. For cars there are a couple of scenarios in which you're b
33 Pihero: A modern anti-skid system is rather complex as it involves three speed or deceleration references : -1/-One from the system itself (BSCU on an Airbus
34 David L: IRS reference makes much more sense to me! Thanks. I was beginning to wonder if it was linked to a cockpit mike and kept maximum braking effect as lo
35 Bri2k1: Sadly, each time I try to correct blatantly erroneous information, my posts get deleted and I am scolded for my insolence. It's great to have a knowl
36 SlamClick: Well said. In years past race drivers would sometimes deliberately spin cars to a stop or before colliding with something. This was usually done when
37 Starlionblue: Indeed. Also, many new cars have "enhanced stabilty" that will differentially apply slight braking pressure while taking a turn at high speed. In suc
38 SlamClick: I don't know why I watch Formula 1 anymore. After watching Worldcup Rally it is almost like watching slotcars. I had no idea how much motor racing ha
39 Mandala499: Handbrake turn on a jet to slow down? Here's one... sometime in Feb2006... Mandala499
40 Starlionblue: Took me years to convince my wife that F1/Indy drivers are actually athletes who need weight and conditioning training just to be able to do their jo
41 Bri2k1: I should point out that this is also incorrect. Friction forces are the result of the coefficient of friction multiplied by the force applied. Surfac
42 SlamClick: Well that would explain the Mu-meter braking action reports! Silly me! I always pictured them measuring how far a cow slid down the runway. Muuuuuuuu
43 David L: Yes. Increase the contact area and you reduce the pressure - same total force, just spread over a bigger area. It's as if you'd never been away.
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based on my experience, but I guess I was just being too subtle...and if I start going down the runway sideways, I'd seriously be thinking about the NTSB or NASA report I'd have to file...as well as concentrating on how to get back on the centerline and under control 
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