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View Full Version : Little planes are big airports...jet wash hazard?



OBIO
January 28th, 2012, 18:02
I was just sitting at KSEA watching the AI traffic come and go...which is a lot more fun now that I am no longer using bone stock FS9 AI stuff. In the line of planes waiting to take off, there were some smaller planes (Beech Baron, C-172, C-182)..mixed in amongst the big birds. And I got to wondering....in real life, when a Cessna is behind a Boeing 737 on the taxiway...and that 737 or whatnot powers up to roll ahead...how much effect does the jet wash have on the Cessna? I have seen footage of the jet wash from a large commercial plane blowing a car, truck, bus like a leaf blower..and it seems to me that a small GA plane would be at risk of being blown away by a large commercial jet.

OBIO

stiz
January 28th, 2012, 19:03
you'd very prolly feel an effect, at it might blow a small aircraft on takeoff, but at taxiway speeds i dont think it'd be any worse than a strong wind. Would be intresting to hear from someone who knows for sure though :)

aeromed202
January 28th, 2012, 19:32
Pros can chime in but I know that in the right conditions, wing tip vorticies can linger for several minutes and still be a problem. I would think that those are of more concern because they wander and can't be seen, as opposed to jet wash that has a predictable location and vector. But after watching people surf the fence at TNCM and Jamie Hyneman testing his tornado tent, I sure would would want some decent spacing.

Wulf190
January 28th, 2012, 19:44
I once did an engine run-up behind a King Air.

I wouldn't recommend it.

Like I said I did that once.

PRB
January 29th, 2012, 04:34
I was told long ago that you want to make sure to land beyond the touchdown point of the big jet if your landing behind one, and if taking off, to take off before the point at which the big jet did. All this to avoid driving through his "wake", which could be bad if you're in a Cessna 150. Taxiing is another matter. Just don't get too close I guess. The force of the wind from high power jets goes down considerably with distance. While working around jets on the flight decks that came up to power to taxi, you really have to be kind of close before you get seriously pushed around. A couple hundred feet back should be safe (famous final words) Never worked around 747s though...

TeaSea
January 29th, 2012, 05:43
Obio,

You're dead on, it's a concern. PRB has described the proper technique. Understand that some aircraft can simply not be operated in certain wind conditions and an artificially induced condition is something to look out for when around larger aircraft.

My personal experience is somewhat limited. The largest airport I've operated out of was Ft. Lauderdale Intl., and the controllers vector the smaller aircraft to a separate runway to avoid this problem....well, that and the fact the GA ramp is on that side.

Hooraw
January 29th, 2012, 06:04
Worked at YYC tower for 30 years, and saw some interesting things. Light powered A/C doing an overshoot on 25 (Westbound), after a wide bodied landed north of 25 on 34. The light A/C did a sudden climb from being lifted by the big-un's right vortices, and 100-200 feet past 34 had to do some correcting (violently) from the down draft from the left vortices. Pretty hairy. Behind anything, prop wash can channel around your A/C and if you are at idle you could get pushed around. Behind a Jet, especially Turbofans, you'd be flying, without control, who knows where! The vortices stop as the big jets have engaged their spoilers, when on the ground. Spacing was 3 miles, within 10-15 miles of Airport, 5 miles when outside of this area and higher up, re:turbulence.
Funniest thing I saw was a pair of coyotes, walking along 25. One old and one young. The old one stopped and sat on his haunches, while Wile trotted to cross 34. That was until a 737 spooled up his engines on the button 34 200 yards south. Wile, spun around and ran faster than a road runner East past in front of the older and I could see the face of the older, I'd swear, he was grinning. LOL

Railrunner130
January 29th, 2012, 06:05
There's a story at work about how the aero club was lost back in the day. Apparently, someone taxied the club airplane (most likely a 172, but I'm not sure) behind a Herk doing power runs. The airplane flipped and that was the end of the aero club. So, yes, jet blast and prop blast will flip small airplanes.

TARPSBird
January 29th, 2012, 11:11
I'll always remember flying commercial out of Itazuke AB in Fukuoka, Japan and seeing the mixed bag of aircraft on the taxiway behind us. JAL Boeing 727, single-engine Cessna type, JASDF T-33, USAF C-118 (not necessarily in that order), and other cats and dogs. Can't imagine what kind of air currents they all had to deal with on take-off, must've been quite a roller-coaster ride. :icon_lol:

pfflyers
January 29th, 2012, 13:58
Obio's original question referred to taxiing behind a jet rather than being behind one that was running up to takeoff power.

I've been in light GA aircraft taxiing behind bizjets like C550s, Lears, and such. Couldn't feel any effect at all.

I would imagine that even in the case of following an airliner type plane, you would have to stick your nose right into the exhaust stream at real close range to feel anything at taxi power settings, especially with the high-bypass type engines in use these days.

CP1207
January 29th, 2012, 14:47
Don't know about a small plane, but here is what can happen to a pickup truck:jump:
Obviously not a normal taxiway situation.
Wake turbulence is not fun.
I was landing a Cessna 172 just after an airliner took off and I was being cautioned by ATC to land short to avoid wake turbulence while at the same time being told to try to expedite as there was a 737 on final behind me. I think that was my 2nd or 3rd student pilot solo cross country flight.

http://www.youtube.com/watch?v=DFP4xl0V0mk

Victory103
January 29th, 2012, 20:50
Something I wish FS would simulate, or at least a ATC "caution wake turbulence". Not fun in a 17,000lb helicopter either.

OBIO,
There is a modified traffic file from PAI I believe that will remove all the GA traffic at your major airports, as generally most will fly into satellite airports. I have a similar set up in FSX to keep the little guys from tangling with the big iron.

SpitXIV
January 30th, 2012, 11:01
The Myth Busters did a show on that not too long ago. Reminds me also about those people that stand at the end
of a runway when the 747's take off.