sleekjet
Posts: 2008
Joined: Sat Jul 28, 2001 1:35 am

### Winter Weather Takeoffs

Assuming an a/c has been properly de-iced, what are the runway parameters during winter storms? In other words, how much ice or snow on a runway does it take to scuttle a flight? And who decides? The pilot? The airport? The airline management?
II Cor. 4:17-18

OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

### RE: Winter Weather Takeoffs

Each type of aircraft has different acceptible performance parameters, so it's difficult to give you a one-size-fits-all type of answer. If I can, what I'll do is give you a general example, which may then vary for a specific type of aircraft.

Snow (or slush) on a runway (commonly referred to as runway "clutter") affects both takeoff and landing performance. For takeoffs, clutter retards normal rates of acceleration, and for landings, braking (DEacceleration) distances are lengthened. The effect of both is that it makes a runway of X-length perform as if it's LESS than X-length, and since the airport folks can't come out and pour additional concrete to extend the runway on short notice   ,aircraft weights must be reduced to keep the aircraft with safe allowable limits. Sometimes, this means that some folks get left behind even though there was an empty seat for them.

Generally speaking, an aircraft may not operate (that's takeoff or landing) on any runway covered by more than 1/2 inch of slush, 1 inch of wet snow, or 4 inches of dry snow. Anything beyond that, and the aircraft does not operate.

For takeoffs below the clutter levels mentioned above, the normal calculated runway takeoff weight is reduced by a factor of 5% or 10%, whether the clutter is minimal, or is closer to the max allowable values.

For landings, the clutter affects the "braking action" of the runway. A dry runway would (obviously) be the best for braking action, and is known as "dry" or "normal". As braking action deteriorates, the classifications range downward from "good", then "fair", then "poor", and finally, "NIL". Aircraft operations are prohibited on "NIL" surfaces, and it should also be noted that operations with "fair" and "poor" reported braking action also entail increasinly more restrictive crosswind limitations.

How is all this stuff measured? That's where things get interesting, as there are both OBjective and SUBjective methods in place.

The airport operator has the responsibility (here in the US, anyways) to have a snow control program in place, and they are generally pretty good about keeping everyone up-to-date of local field conditions. Some of this accomplished via issuance of a NOTAM (notice to airmen), but some stuff changes so quickly, that tower issues the information.

For takeoffs, snow depth is mostly commonly reported (objectively) by airport folks actually out there. A pilot can certainly make a depth determination, but obviously, doing so from from purely within the cockpit is a more subjective endeavor.

For landings, braking action can be assessed by either specially-equipped vehicles (that provide a numerical reading like MU, or other, that can be converted to good/fair/poor/NIL), or the pilots of any landing aircraft can report the braking action they experienced when they landing. Given the above two mechanisms, it's easy to see that one has more opportunity for subjectivity than the other.

Considering all the information above, who makes the decision? It sort of depends. If the airport operator decides that the clutter has exceeded limits and then closes the runway for plowing/brooming/de-icing, it's a no-brainer. That aside, here in the US, under FAR 121 Domestic/Flag rules, the captain and/or aircraft dispatcher make the call. If one of those two thinks they have limits, but the other has more current info that says they don't, the most conservative info takes precedence. I know there are probably some crews out there who will disagree, but I can assure you that within my 23-year career, I have personally told crews NOT to land on occasion because I had more timely info than they did. Does't happen often that way, but it does happen.

Sorry to be so long, but a complicated question...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.

sleekjet
Posts: 2008
Joined: Sat Jul 28, 2001 1:35 am

### RE: Winter Weather Takeoffs

Thanks, man, for maybe the best, most detailed response in the history of airliners.net.

Do you work at DFW?
II Cor. 4:17-18

OPNLguy
Posts: 11191
Joined: Tue Jun 15, 1999 11:29 am

### RE: Winter Weather Takeoffs

Thank-you kindly...

Yep...

Another related factor in winter ops is plowing. At BUF last week, it was coming down so hard that they couldn't even see enough to plow, so off the runway they came. Once they eventually got back out there, there was so much accumulation (2-4 inches per hour) that it took them forever to get the runway, taxiways, and ramp areas cleared off enough to operate. Oh yeah, more heavy snow off and on the entire week. Something like 80 inches total...

ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.

Bicoastal
Posts: 2446
Joined: Wed Oct 06, 1999 5:56 am

### RE: Winter Weather Takeoffs

Prague had plenty of snow when I departed there on Sunday around noon. The runway was closed off and on most of the morning, but the equipment (BA 767) on which I was to fly out arrived on time. On my take-off, the British Airways 767, fully loaded with passengers, had a very short take off roll and handled the snowy runway just fine. I was supposed to be on a Lufthansa flight back to the USA via Frankfurt, but their equipment never left Frankfurt for Prague due to the snow storms. Hmmmm....do British pilots have more ability than Lufthansa's.....???? In any case, Lufthansa's personnel in Prague handled the cancellation very well. They rebooked me on BA to London then on my favorite United Airlines from London to the USA.
Airliners.net has many forums. It has spell check and search functions. Use them before posting!

Maniac
Posts: 109
Joined: Mon Apr 30, 2001 8:36 am

### RE: Winter Weather Takeoffs

I had a flight out of PWM when the pilot went out in a plow truck with the snow removal crew to check the runway. He said that on landing the previous flight, the braking action was not good enough, and he wouldn't take off until he saw the runway.

### Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos