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Tailwind limitations

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Tailwind limitations

Old 15th Jun 2008, 16:52
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Tailwind limitations

Whilst I fully appreciate that a tailwind causes heavy performance penelties, I would like to ask whether a limitation is always necessary.

To demonstrate with an example, does a PA-28 have any problem to land at Edwards AFB (15000ft) with a 15kt tailwind if its tailwind limit is 10kts? Similarly for takeoff.

Shouldn't today's commercial aircraft have tables for actual conditions at a particular airport to work out the actual limit, rather than a fixed limit for all conditions?

I cannot stress enough the critical effects a tailwind has on takeoff and landing performance, but I feel that with today's world of LPCs, much more can be done with actual conditions.

This can be especially important in airports like Lourdes Tarbes, where landing and take-off can only be performed in opposite directions.
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Old 15th Jun 2008, 17:18
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there could be issues with excess stress on the struts/ brake energy, or tire speed limits, due to excessive ground speed---so, it's best to stay within the limits of charted POH performance---unfortunately in aviation you get what you pay for---you can't really safely go IFR with embeded TS's w/o weather detection of some advanced sort---or really operate practically without a transponder or radio???---no CAT111 ILS in a Baron---Pilots who operate for the forest service sometimes have to wait days for the right density altitude/performance conditions to make a gettaway in the likes of Montana ---Oregon--etc.

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Old 15th Jun 2008, 17:58
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To illustrate PA's post

I witnessed a Cub flying approx. 15 feet above the runway on runway heading, BACKWARDS. In the 45knot Headwind, he could have touched down and had a NEGATIVE ground roll. With Tailwheel, that's akin to backing doubles. If he had reversed heading, he would have had a Groundspeed of close to Vne. Inside each of these possibilities is the very real need to consider ALL your aircraft's capabilities and drawbacks.

Old 15th Jun 2008, 18:55
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As usual probably depends what you pay. Some of our 737s are certified up to 15 kts tailwind, most only up to 10 kts. I guess you have to pay a little extra to get that, same as you need to pay a bit more to get 10 or 15 minutes of take off power instead of 5.
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Old 15th Jun 2008, 23:20
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Once time I scared myself by taking 5 kts tailwind on single prop on take off. The ground roll distance wasn't the problem but the usual wind speed increase with the altitude was the problem. I had wicked ground speed with same rate of climb... Thus shallower climb over the ground.

Also the building in front of me didn't move with the wind.
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Old 16th Jun 2008, 21:15
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It is all about paying for the performance data. I used to fly A320's that were certified to 15 kts tailwind, but our A319's were only good to 10 kts. If you are willing to spend the money you can get a plane certified to do about anything within its physical capabilities. One extra problem you can run into with jets and tailwinds is tire speed limits.
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Old 16th Jun 2008, 22:56
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On the one hand you suggest Certification is merely a money game, performance certified depending on payment to..... Whom? Then you claim that performance limits of Aviation wheels and tyres are made within limits of five knots? I'm kind of hoping I merely misunderstand you, because one of us is certifiable if I'm reading you correctly.
Old 16th Jun 2008, 23:28
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Minor points ..

(a) tailwind includes a 50% penalty .. ie 10kt in the AFM is 15kt for the certification, etc

(b) the regulators treat 10kt tail as a very hard limit for certification unless the OEM jumps through a bunch of hoops .... problems can involve brake energy, directional control on slippery runways, unexpected pitch up at brakes release ...

(c) reality is that the OEM has to jump through a bunch of hoops to certificate anything and everything .. you want something extra, you pay for it. For instance, we did a DC9 engine T/O limit extension years ago to provide a bit extra for mum and the kids and corporate sleeping patterns .. local regulatory approval to run to the 10 minutes .. but no credit for it re the RTOW sums ... negligible cost. Had we got the full implementation from DAC ... lots of dollars for not enough operational benefit to justify ...

(d) the added dollars go to the OEM ... quite a normal arrangement for add on requirement approvals ...
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Old 17th Jun 2008, 00:47
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Not so minor, J_T. As an OEM, we get many requests for equipment, performance certification right up 'til the question, "what are you willing to pay?" Suddenly, the modification is not so important.

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Old 17th Jun 2008, 04:47
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... spoken, good sir, like a true OEM representative ... good health !!
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