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Spacing Behind Heavys - On The Taxiway?  
User currently offlineN353SK From United States of America, joined Jun 2006, 822 posts, RR: 0
Posted (7 years 1 month 2 weeks 1 day 23 hours ago) and read 3009 times:

After viewing this photo:



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I began to wonder if there is a set protocol regarding small aircraft being behind large aircraft on the taxiway. Is there ever a risk of a large aircraft (say, a 777) producing so much thrust while taxiing that a smaller aircraft is in danger of being, for lack of a better term, "blown away?" I have an image in my head of a 777 applying thrust to move forward and a Cessna 152 blowing away like a leaf in the breeze. Does ATC tell small aircraft to beware or is it the pilot of the small craft's responsibility to tread lightly?

12 replies: All unread, jump to last
 
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 1, posted (7 years 1 month 2 weeks 1 day 23 hours ago) and read 3004 times:

Quoting N353SK (Thread starter):
risk of a large aircraft (say, a 777) producing so much thrust while taxiing that a smaller aircraft is in danger of being, for lack of a better term, "blown away?"

Absolutely......I've been well behind an E45X on a taxiway when they have powered up to move and been shaken quite a bit in a C210. I always try to avoid having the fuselage at a 90 degree angle to any larger aircraft.

Quoting N353SK (Thread starter):
Does ATC tell small aircraft to beware or is it the pilot of the small craft's responsibility to tread lightly?

I've always told smaller aircraft to be aware.....a requirement, no, not unless they changed the book again and didn't tell everyone!



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineMir From United States of America, joined Jan 2004, 21634 posts, RR: 55
Reply 2, posted (7 years 1 month 2 weeks 1 day 22 hours ago) and read 2991 times:

Quoting IAHFLYR (Reply 1):
a requirement, no, not unless they changed the book again and didn't tell everyone!

There's a little note in 7110.65 3-7-3 which says "use caution when taxiing smaller aircraft/helicopters in the vicinity of larger aircraft", as well as a sentence saying that clearances that require heavy jet aircraft to use greater than normal taxiing power should be avoided, and that small aircraft shouldn't be moved too close to taxiing or hover-taxiing helicopters.

That's about all I could find. I thought there was some sort of jet blast warning (or at least phraseology) in there, but couldn't find it.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineDw747400 From United States of America, joined Aug 2001, 1260 posts, RR: 1
Reply 3, posted (7 years 1 month 2 weeks 1 day 19 hours ago) and read 2931 times:

Quoting N353SK (Thread starter):
Is there ever a risk of a large aircraft (say, a 777) producing so much thrust while taxiing that a smaller aircraft is in danger of being, for lack of a better term, "blown away?"

In an interesting story tangentally related to your question:
Upon completing my PPL checkride, we parked next to a very big, very old Sikorsky (an S-61 I think) that, at the time, was getting ready to taxi out. Not knowing this, the examiner told me to park right next to him. In short, we had two people sit in the 172, with another two people holding the wing struts, but we still rocked and rolled when that chopper started to taxi.

Obviously, thats very different than a big jet, but in terms of moving large volumes of air very fast, a chopper rotor or a GE90 can both make for an interesting day.



CFI--Certfied Freakin Idiot
User currently offlineSpruit From United Kingdom, joined Oct 2005, 375 posts, RR: 0
Reply 4, posted (7 years 1 month 2 weeks 1 day 15 hours ago) and read 2885 times:

Quoting N353SK (Thread starter):
I began to wonder if there is a set protocol regarding small aircraft being behind large aircraft on the taxiway. Is there ever a risk of a large aircraft (say, a 777) producing so much thrust while taxiing that a smaller aircraft is in danger of being, for lack of a better term, "blown away?"

I think in relation to that picture you've posted the spacing is okay, but I for one, certainly wouldn't like to be taxying anything GA sized behind that T7 considering at idle thrust the GE90-115B exhaust velocities are about 30-50MPH!

Spru!



E=Mc2
User currently offlineHAWK21M From India, joined Jan 2001, 31684 posts, RR: 56
Reply 5, posted (7 years 1 month 2 weeks 1 day 14 hours ago) and read 2872 times:

Thats the Airport I work at.
Its the Angle of the photo thats giving the impression that they are very close up.The Pic is taken from a hill around 75 meters away & on a height of 100-150 feet.Also Taxiing out the B773ER would not be ramming up the thrust levers fwd as what one would think.
Adequate spacing is always maintained.
regds
MEL



Think of the brighter side!
User currently offlineIAHFLYR From United States of America, joined Jun 2005, 4790 posts, RR: 22
Reply 6, posted (7 years 1 month 2 weeks 1 day 11 hours ago) and read 2818 times:

Quoting Mir (Reply 2):
There's a little note in 7110.65 3-7-3 which says "use caution when taxiing smaller aircraft/helicopters in the vicinity of larger aircraft", as well as a sentence saying that clearances that require heavy jet aircraft to use greater than normal taxiing power should be avoided, and that small aircraft shouldn't be moved too close to taxiing or hover-taxiing helicopters.

Yes, but it is not a requirement to advise, simply a requirement to avoid issuing those type of clearances, but still a nice heads up to the small plane driver.



Any views shared are strictly my own and do not a represent those of any former employer.
User currently offlineATCT From United States of America, joined Mar 2001, 2293 posts, RR: 38
Reply 7, posted (7 years 1 month 2 weeks 1 day 10 hours ago) and read 2782 times:

Yea there is no requirement telling me I cannot taxi a Cessna 172 (or even an ATR / Saab 340) behind a B772.

Now say when I launch a 777 and my next aircraft ready to go at the hold short is an ERJ or Saab etc., I'll usually say "Colgan 5435, Houston tower, runway 15L, 'your discretion' position and hold for wake turbulence" Some people like it, some people dont, but the way I look at it, if he rams the throttles and shoots out a second after the 777 has started to roll and something happens, Im clear.

Anywho as Mir stated, the only "requirement" I have is not to put a small or small + in position behind a departing heavy aircraft. (Less than 44,000lbs would be a small / +)

"3-7-3. GROUND OPERATIONS

WAKE TURBULENCE APPLICATION

Avoid clearances which require:

a. Heavy jet aircraft to use greater than normal taxiing power.

b. Small aircraft or helicopters to taxi in close proximity to taxiing or hover-taxi helicopters."

----

As one who has read alot of the 7110.65 in the past few years, this seems to be very vague. "Avoid Clearances" leaves open that you can still do it. I believe "Clearance shall not be given which require:" would be better if you could NOT do these at all. So what im thinking is you can do it, but just use caution.

Anywho thats my 2 Cents.

ATCT

(Note: This is all speculation and personel interpretation, not an official answer or guide, I will look into this matter more deeply at work)



"The way to get started is to quit talking and begin doing." - Walt Disney
User currently offlineMark5388916 From United States of America, joined Aug 2007, 377 posts, RR: 0
Reply 8, posted (7 years 1 month 1 week 6 days 10 hours ago) and read 2563 times:

Not quite the same but you can see what happens to a F-16 when it taxis too close to a B-1.



Mark

EDIT: I took this video off this thread B-1 Gets An F-16 Kill (by BladeLWS Jun 25 2007 in Military Aviation & Space Flight)

[Edited 2007-08-09 17:22:46]


I Love ONT and SNA, the good So Cal Airports! URL Removed as required by mod
User currently offlineChksix From Sweden, joined Sep 2005, 345 posts, RR: 4
Reply 9, posted (7 years 1 month 1 week 6 days 10 hours ago) and read 2556 times:

Interesting that the photographer missed it completely and filmed the takeoff instead!


The conveyor belt plane will fly
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 10, posted (7 years 1 month 1 week 6 days 9 hours ago) and read 2536 times:

Quoting Chksix (Reply 9):
Interesting that the photographer missed it completely and filmed the takeoff instead!

"The board finds that the videographer lost situational awareness and, as a result, did not see the F-16 until it was too late."

* * *


Pilots of large jet airplanes are aware that they continue to be responsible for damage done by their jet blast. Almost everywhere in the world, all it takes to get rolling is just to release the brakes. There are a few exceptions of course. If the taxiway runs uphill it make take some handles-forward to get rolling. San Jose California, holding short of 32L used to be on asphalt and planes would sink in on a warm day. Other planes would "fall in" to the holes and require a lot of thrust to crawl up out of them. It was a very good idea not to place yourself right behind them.

As I once asked a Cessna pilot: If my engines will make my 180000 pound airplane fly five hundred miles per hour how fast will they make your two thousand pound airplane fly?



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineSmcmac32msn From United States of America, joined May 2004, 2211 posts, RR: 4
Reply 11, posted (7 years 1 month 1 week 6 days 9 hours ago) and read 2523 times:

Quoting SlamClick (Reply 10):
"The board finds that the videographer lost situational awareness and, as a result, did not see the F-16 until it was too late."

I didn't know we all came to that concensus, but I'm fine with that.



Hey Obama, keep the change! I want my dollar back.
User currently offlineCeph From Singapore, joined Jun 2007, 141 posts, RR: 0
Reply 12, posted (7 years 1 month 1 week 1 day 9 hours ago) and read 2279 times:

oops... how did they right the F-16? Did the plane get damaged?

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