Reduced Thrust vs. Contaminated Runway
Thread Starter
Joined: Feb 2001
Posts: 243
Likes: 1
From: Milkway Galaxy
Reduced Thrust vs. Contaminated Runway
Hi,
By Regulations (e.g JAR 25), reduced thrust method on TO (i.e Assumed Temp or Flex) is not allowed on contaminated runways.
What is the physical reason behind that?
Any idea.
Thanks in advance
By Regulations (e.g JAR 25), reduced thrust method on TO (i.e Assumed Temp or Flex) is not allowed on contaminated runways.
What is the physical reason behind that?
Any idea.
Thanks in advance
Joined: Dec 2002
Aviation Qualifications: ATP+Mil
Posts: 3,985
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From: Where the Quaboag River flows, USA
Contaminated runway calculations are inherenly guesstimates, so the regulators want to ensure the best power to eliminate an errors. Contamination can have a large and uncertain drag on the take-off run. This restriction has been applied to all transport category planes I have flown, civil and military
GF
GF
Joined: Sep 1999
Posts: 5,552
Likes: 25
From: ME
In FAA-Land there are no contaminated runways, they dont get snow or ice or any other nasty stuff, therefore aircraft are not certified for operations on contaminated runways, the aircraft FLIGHT manual only contains certified data such as reduced thrust performance.
When airlines discovered that they were operating in a world that was very different to FAA-land, they insisted that the manufacturers gave them "SOME" data for operating on contaminated runways, the manufacturers decided as they weren't required to certify contaminated data, they would use the characteristics associated with contaminated runways that were developed by NASA using a Convair 880 aircraft. They then put this data as "ADVISORY" in the aircraft OPERATIONS MANUAL, which isn't a certified document.
The risk of operating on contaminated runways therefore lies with the airline and not the manufacturer. If any airline decided that they wanted contaminated data combined with assumed/flex and they had sufficient "Purchasing clout".... they could get the manufacturer to include that data.
But considering that a contaminated runway usually isnt 100% accurately reported, would you really want to take the additional risk of using Flex temperature?
Mutt
When airlines discovered that they were operating in a world that was very different to FAA-land, they insisted that the manufacturers gave them "SOME" data for operating on contaminated runways, the manufacturers decided as they weren't required to certify contaminated data, they would use the characteristics associated with contaminated runways that were developed by NASA using a Convair 880 aircraft. They then put this data as "ADVISORY" in the aircraft OPERATIONS MANUAL, which isn't a certified document.
The risk of operating on contaminated runways therefore lies with the airline and not the manufacturer. If any airline decided that they wanted contaminated data combined with assumed/flex and they had sufficient "Purchasing clout".... they could get the manufacturer to include that data.
But considering that a contaminated runway usually isnt 100% accurately reported, would you really want to take the additional risk of using Flex temperature?
Mutt
Joined: Dec 2002
Posts: 2,776
Likes: 353
From: UK
AFAIR neither of the ref documents below answers the question directly, but there is plenty of information.
Reduced Thrust Takeoff
Takeoff / Landing on Wet, Contaminated, and Slippery Runways
Reduced Thrust Takeoff
Takeoff / Landing on Wet, Contaminated, and Slippery Runways
Thread Starter
Joined: Feb 2001
Posts: 243
Likes: 1
From: Milkway Galaxy
Thank you all for answers.
I was considering to relate my question to the "weird" effect of contamination on V1 speed. I called it "weird" because the contamination is considered to have additional decelerative effect if decision is "Stop" at V1 or difficulty in acceleration if decision is "Continue" at V1. These are just oppsoite effects which are considered in Wet/slippery runway at which reduced thrust can be done. After all these, I thought this "weirdness" somehow may be preventing reduced thrust method to be used because of Vmcg. But now I understand no conculusion of my thoughts.
Thank you again.
I was considering to relate my question to the "weird" effect of contamination on V1 speed. I called it "weird" because the contamination is considered to have additional decelerative effect if decision is "Stop" at V1 or difficulty in acceleration if decision is "Continue" at V1. These are just oppsoite effects which are considered in Wet/slippery runway at which reduced thrust can be done. After all these, I thought this "weirdness" somehow may be preventing reduced thrust method to be used because of Vmcg. But now I understand no conculusion of my thoughts.
Thank you again.
