Corporate Jet Performance?

[Bob Turner]

It has been a quarter century since I touched a jet. Here's a performance question for those with more recent experience:

Today we had a Citation request our longer runway. His choice was 3400' runway with a ten knot headwind or a 4400' runway with a ten knot tailwind.

Not having any analyses left over from the olden days I cannot begin to form an opinion on this one. Anybody have data on runway requirements in +/- 10 knot wind? 20 knots sounds like a lot when your touchdown speed is 90 knots.

 

[Bob Turner]

I might have found some “Bravo” analyses. Have to open the big computer. There is some indication that headwinds affect actual landing length by about 10% for each 4 knot increment.

I recall that in the 737 our actual max allowed tailwind was ten knots, but do not recall wind otherwise in the analysis.

 

[Bob Turner]

Answering my own question:

In summary, using these two POHs as examples we can begin to develop some rules of thumb:
• Each knot of headwind component on takeoff improves takeoff performance by roughly one percent, while each knot of tailwind component degrades performance by three to five percent. Tailwinds are three to five times as detrimental to takeoff as headwinds are an improvement.
• While each one knot of headwind component improves landing performance by about one percent, each knot of tailwind component degrades landing distance by about three to five percent. Tailwinds are roughly three to five times as effective at altering landing performance thank headwinds...and the alteration is not in your favor.
• In almost all cases, then, there is very good reason for avoiding tailwind takeoffs and landings, even if it makes more sense for the . . .

This came from an FAA site. It first discussed Hawker-Beech runaround charts, then this from both Bonanza and C-172 POH.

Unfortunately, the Hawker data was takeoff only - but the trend is identical. Ten knots gives you 10% advantage on takeoff, but 32% disadvantage if it is a tailwind.

 

[Bob Turner]

Here is my analysis:

So, we can work backwards - a 4400 foot landing roll with a ten knot tailwind would mean you can land in 3333’ no wind, or 3000’ with ten knots headwind.

So you have 400’ to spare using 28R, but zero to spare using the longer 10 L.