Wake Turbulence Avoidance

[phantomwray]

Here's the scenario:

You are in a Cessna 172 and are taking off after a large passenger jet which is also taking-off. You note where it rotates so you can plan to remain above it's flight path. The tower then clears you for take-off after a very short delay. I know you can decline the clearance if you feel it is not safe. Assuming that you do want to accept, if you rotated in your 172 at the same point as the jet, but then climbed out at your best angle of climb speed, would your flight path remain above that of the jet's? Since the jet is travelling much faster, it's departure slope would be much shallower than yours, so there shouldn't be any problems. Am I correct?

[static]

No, you`re not correct.. .Be very, very careful when taking off behind a big one.. .You will never ever be able to stay above his climb path. He will be climbing with 2000 feet/min or close to it. Just take your time. At least 2 min, but if it were me I`d stick closer to four min.

[RadarContact]

Sorry to tell you, but you're NOT correct! Assumptions like this may well be your last one. Airspeed alone is not an indication of climb gradient, unless used together with the climb rate - and you would need C-130-Boosters to beat a 737 there!

The only way to be safe is when you are sure to be able to liftoff well before the point were the 737 rotates and then immediately make a turn into the wind (crosswind departure) - I admit, not always an option at bigger airports.

[phantomwray]

Okay, thanks for the backup guys. Just after I posted, I did up some sample calculations to find the approximate angle that my Cessna and an imaginary jet make with the ground during climb-out. Obviously the Cessna's was much lower. Before though, it just seemed to me that even though the jet was climbing at thousands of feet per minute, it's forward velocity being as high as it is would make it's departure slope lower. Of course I wouldn't ever try to cut things this close, but I was just curious and wanted to know if it was possible. Thanks! <img src="smile.gif" border="0">