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Bad Weather Limitations

Mon Dec 22, 2003 5:03 pm

Yesterday early morning when I arrived to Amsterdam from Brussels the weather was quite bad, with a lot of strong wind, heavy rain and turbulence. We flew in a Fokker 70 and it was one of the most "funny" landings I have ever experienced (after accumulating more than 1 million miles so far).

I noticed that flights on Fokker 70's were operating as scheduled, but flights on Boeing 737's were delayed. I did not find information about other aircraft types.

My questions are:

1) Is there a significant difference between airplane types and models regarding the maximum cross wind, wind velocity, and other bad weather conditions that the are authorized to take off and land in?

2) Generally speaking, can bigger / heavier aircraft operate in worse weather than smaller aircraft? Or can smaller aircraft like the F70 operate in worse weather than big planes because they are easier to control and more responsive?

3) Are the bad weather limits something determined by the airlines or by the authorities?

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Joined: Sun Sep 24, 2000 12:26 pm

RE: Bad Weather Limitations

Mon Dec 22, 2003 5:59 pm

Just a side note too many a time I noticed that B737s made it down in severe weather and wind conditions but you'd see the likes of A330s, B767s, B777s, A340s diverting? Only the B747s and B734s made it down nicely!
Boeing747 万岁!
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Joined: Wed Aug 29, 2001 8:47 pm

RE: Bad Weather Limitations

Mon Dec 22, 2003 7:42 pm

Mr. BA...
Well, in some place in this world... when bad weather comes in, the 737s made it, the 747s made it, the 757/767s made it, the 777s made it, the A300s and A310s made it... the A319s made it, the 320s made it, but the 321s are the only one left holding! Big grin

When losing situational awareness, pray Cumulus Granitus isn't nearby !
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RE: Bad Weather Limitations

Tue Dec 23, 2003 12:25 am

Its not just a matter of the aircraft model. There is the issue of equipment and the destination.

If an aircraft doesn't have the equipment required to perform a landing to the particular landing weather conditions, it will not do it.

The various categories of weather minima require various equipment. Not all aircraft are equipped with equipment to perform landings in all categories.

As for size, larger aircraft tend to be more stable in rough weather, but once you consider aircraft that are over 20,000 pounds its not usually a factor.

RE: Bad Weather Limitations

Tue Dec 23, 2003 1:08 am

When it comes to "bad weather" limitations, bigger isn't always better. Over the years, hundreds of people have been killed in windshear related accidents on one of the big factors in these type accidents is aircraft size. To put it simply, large, heavy aircraft are affected considerably more by windshear than smaller, lighter aircraft. It's high school physics - mass and inertia. Larger, heaver aircraft have more inertia to overcome which makes it harder for them to accelerate relative to the airmass that they are flying in. Light aircraft have less inertia to overcome plus they usually have the advantage of "instant" airflow over the wings when power is applied.

What this means is that large aircarrier type aircraft are more susceptible to windshear than smaller jets and light aircraft. In fact, I can't honestly remember any corporate jet ever being lost to windshear. Same thing applies to light aircraft. Not to say that it hasn't ever happened, it's just extremely rare.

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RE: Bad Weather Limitations

Tue Dec 23, 2003 1:56 am

There are several factors involved here.
1. Low visibility issues. This is related to 3 factors. The airport facility and its capability, ILS, GPS or what it has for instrument landings. The aircraft and what it is equipped for, and the crew's qualifications. For example, for a CAT IIIA approach down to 600 foot visibility minimums, everything has to be qualified down to that level. If it is not, then the minimum visibility is raised accordingly. For example, if a Captain is new and has few hours on that particular type, then his minimums are raised. So each individual aircraft and flight may have a different situation. Some airlines also elect not to spend the money to get the best qualifications/lowest minimums. Its a business decision.

2. Then there are the wind conditions. Each aircraft type has a maximum demonstrated crosswind and limiting tailwind. Although usually landing in a headwind, the approach must meet those conditions. Also, many carriers, when there is turbulence, recommend additional speed adjustments on approach to compensate. All of this makes an approach more difficult, and individual crews may decide not to chance an approach depending on their comfort level even if they are within limits.

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