landing jet on Snow covered runway ABS or none
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landing jet on Snow covered runway ABS or none
Writing this from Eindhoven. had to divert in here this morning in heavy snow as destination went down very quickly.
Here was 300 feet and 800 meters and the runway had white out with snow.
Runway was long for a citation so I braked very carefully feeling the ABS unlocking the wheels.
On snow covered runways or icy runway are you better switching ABS off?
pace
Here was 300 feet and 800 meters and the runway had white out with snow.
Runway was long for a citation so I braked very carefully feeling the ABS unlocking the wheels.
On snow covered runways or icy runway are you better switching ABS off?
pace
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This one is a 550 and no reverse thrust.
ABS is normally a bad idea on snow or ice and it can be switched off! But cannot find any reference to ABS on or off on snow or Icy surface ?
Normally clear of runway after landing or below 30 kts it ABS off anyway.
Pace
ABS is normally a bad idea on snow or ice and it can be switched off! But cannot find any reference to ABS on or off on snow or Icy surface ?
Normally clear of runway after landing or below 30 kts it ABS off anyway.
Pace
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I seem to recall that under 5kts gs it will not work - simply locks the wheels. Long time since I flew the 550 but there should however be a reference to it in your flight manual or the POH.
The anti-skid system on Citation aircraft is not as sophisticated as ABS on you average family car, so beware!
ABS on even a cheap car will brake the wheels until adhesion is momentarily lost, then momentarily release the brakes until adhesion is regained, and repeat the process until brake pedal pressure is released by the driver. The result is high frequency cadence braking, whereby the car tyres penetrate water or light snow and remain in contact with the tarmac, giving maximum braking deceleration.
The anti-skid system in Citations just assumes a skid is about to occur if the main gear wheel rotation speed drops below what it would be if the aircraft was taxying (in dry conditions) at fast walking pace, then opens a valve to reduce the maximum brake pressure the pilot can apply. So if the pilot brakes hard on a slippery surface causing the wheel rotation speed to drop below the preset limit, a valve opens reducing the hydraulic pressure in the braking circuit, until the rotation speed increases above the trigger point again. The resulting braking effect is nothing like as effective as car ABS, as the tyre can continue to aquaplane.
So if you really need to stop quickly in heavy rain or light snow in an emergency, turn off the anti-skid. You will at least have a chance that the tyres might bite through the water/snow to the surface below. You might have a job maintaining directional stability, and might well blow a tyre, but you will have a better chance of stopping.
Obviously this is not what Cessna recommend. They would rather you skid off the end of the runway and die in a fireball so that their clever lawyers can blame you for landing on an inaccessible runway.
ABS on even a cheap car will brake the wheels until adhesion is momentarily lost, then momentarily release the brakes until adhesion is regained, and repeat the process until brake pedal pressure is released by the driver. The result is high frequency cadence braking, whereby the car tyres penetrate water or light snow and remain in contact with the tarmac, giving maximum braking deceleration.
The anti-skid system in Citations just assumes a skid is about to occur if the main gear wheel rotation speed drops below what it would be if the aircraft was taxying (in dry conditions) at fast walking pace, then opens a valve to reduce the maximum brake pressure the pilot can apply. So if the pilot brakes hard on a slippery surface causing the wheel rotation speed to drop below the preset limit, a valve opens reducing the hydraulic pressure in the braking circuit, until the rotation speed increases above the trigger point again. The resulting braking effect is nothing like as effective as car ABS, as the tyre can continue to aquaplane.
So if you really need to stop quickly in heavy rain or light snow in an emergency, turn off the anti-skid. You will at least have a chance that the tyres might bite through the water/snow to the surface below. You might have a job maintaining directional stability, and might well blow a tyre, but you will have a better chance of stopping.
Obviously this is not what Cessna recommend. They would rather you skid off the end of the runway and die in a fireball so that their clever lawyers can blame you for landing on an inaccessible runway.
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Eindhoven is long so was not worried a outrunning out of runway. A 737 landed behind but yes the runway had a complete cover of snow and the brakes kept releasing.
It was then best to take your feet off brake pressure and reapply.
It crossed my mind in the rollout to flick the ABS off
Pace
It was then best to take your feet off brake pressure and reapply.
It crossed my mind in the rollout to flick the ABS off
Pace
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Obviously this is not what Cessna recommend. They would rather you skid off the end of the runway and die in a fireball so that their clever lawyers can blame you for landing on an inaccessible runway.
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aerobat77
Not anywhere near as fantastic as your reply though. I have read it several times and have no idea what you want to get accross to us, "keep just out of virtual trouble when you have time" whats all that about??? Cute???? Proud?????
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7th Dec 2012 13:56
Writing this from Eindhoven. had to divert in here this morning
somebody lands the bizjet on the alternate and not the destination and the first thought he has is to post via his phone on pprune and express his thoughts and doubts about antiskid on snowy runways
Q:Whats more dangerous than no Anti-Skid ?
Jumping to conclusions...
Last edited by His dudeness; 9th Dec 2012 at 15:35.
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I cannot believe some of these replies.
Pace, I don't fly a Citation but I would have thought using the ABS option on a slippery surface would be a good idea. But what do I know. Maybe I will learn something from some intelligent replies.
Pace, I don't fly a Citation but I would have thought using the ABS option on a slippery surface would be a good idea. But what do I know. Maybe I will learn something from some intelligent replies.
Last edited by Richard Westnot; 9th Dec 2012 at 16:28.
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Aerobat 77
Fail to see what is funny? We had to divert due to a number of airports being closed as did quite a few other aircraft!
Eindhoven was offered which has a long runway for something like a Citation!
A 737 landed behind us so I would be more worried landing that on a runway which was pure white.
The anti skid was struggling meaning I was very gentle on the brakes releasing and reapplying!
Normally on cars anti skid does not do a good Job on snow or ice !
On the Citation you can switch anti skid off!
I wondered in those conditions whether anti skid would have been better on or off.
I do have pictures of the conditions which I can put up so you can see how realistic MSFS has become nowadays
Pace
Fail to see what is funny? We had to divert due to a number of airports being closed as did quite a few other aircraft!
Eindhoven was offered which has a long runway for something like a Citation!
A 737 landed behind us so I would be more worried landing that on a runway which was pure white.
The anti skid was struggling meaning I was very gentle on the brakes releasing and reapplying!
Normally on cars anti skid does not do a good Job on snow or ice !
On the Citation you can switch anti skid off!
I wondered in those conditions whether anti skid would have been better on or off.
I do have pictures of the conditions which I can put up so you can see how realistic MSFS has become nowadays
Pace
Last edited by Pace; 9th Dec 2012 at 17:28.
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The antiskid was doing what it is supposed to do...release to avoid locked wheels. I wouldn't turn it off, or you would increase the likely possibility of a flat tire should you experience a portion of the runway with increased friction.
No reverse is a big issue in a jet on a contaminated runway. You would be better off shutting down an engine to reduce idle thrust on the rollout than turning off the antiskid...in my opinion.
No reverse is a big issue in a jet on a contaminated runway. You would be better off shutting down an engine to reduce idle thrust on the rollout than turning off the antiskid...in my opinion.
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Can't remember if it was early Citation or Mitsubishi Diamond but in any rate anti skid was "working" by releasing the pressure in a very quick manner until the brakes were completely gone. After releasing the brake pressure the same cycle was completed. More than once I was switching the anti skid off on slippery iced up runways.
Last edited by bluesafrica; 9th Dec 2012 at 18:49.
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The anti skid was struggling meaning I was very gentle on the brakes releasing and reapplying!
This is from the CJ3 FSI Manual since Iīm to lazy to go to the cellar to dig the old 550 manual out...
To ensure optimum braking on water, snow, and ice-covered, hard-surface runways and all unimproved surfaces, it is necessary for the pilot to apply maximum effort to the brake pedals throughout the landing/or abort run.
Normally on cars anti skid does not do a good Job on snow or ice !
Last edited by His dudeness; 9th Dec 2012 at 18:58.
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What to keep a troll kid amused ?
I am sure you have MSFS to go and play with and keep you amused.
Just shows your utter ignorance of corporate flying! Once the PAX are dispatched we often have hours of boredom awaiting their return and either post to pprune on the computers in the pilot lounge or YES an I phone.
Pace
Pace
I am sure you have MSFS to go and play with and keep you amused.
worries with the big paying passengers and the company than to think about the use or no use of antiskid and post it here via phone entirely from the airport .
Pace
Pace
Last edited by Pace; 10th Dec 2012 at 10:48.
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Car ABS is designed to facilitate steering under breaking on slippery surfaces. It is well known that car ABS slightly decreases the maximum deceleration possible, but it allows you to steer round a hazard. We don't need to do that in the same way.
I have never come across an aircraft anti-skid which judders the brakes on and off - They have always applied the maximum braking to just short of the point where it would lock the wheels, and held that braking force. This gives the maximum deceleration.Turning off the anti-skid seems a bad idea to me.
I have never come across an aircraft anti-skid which judders the brakes on and off - They have always applied the maximum braking to just short of the point where it would lock the wheels, and held that braking force. This gives the maximum deceleration.Turning off the anti-skid seems a bad idea to me.
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Aerobat77, what was the point you were trying to get across? What so cute or funny about the post?
The guy landed on a snow covered runway and asked what to me seemed like a reasonable question. Apart from stating the obvious (maintain directional control, and a misspelt reference to runway length), your post served no useful purpose, so why highlight to everyone that you probably DO only fly Microsoft products?
The guy landed on a snow covered runway and asked what to me seemed like a reasonable question. Apart from stating the obvious (maintain directional control, and a misspelt reference to runway length), your post served no useful purpose, so why highlight to everyone that you probably DO only fly Microsoft products?