Head something from ATC today I didn't like.., .

Pinstriper

Pinstriper

Pre-takeoff checklist
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Pinstriper
Heard something from ATC today I didn't like.., .

On a flight from O22-OVE today while at 6,500' NorCal comes on and tells me an MD80 was gonna cross my path at 8,000' "caution wake turbulence".
I responded with I was going to decend to 4,500'.. All the while wondering when I was gonna be hit with anything. So my question is what would you have done? I assumed I took appropriate action and aside from mechanical turbulence we felt nothing.. I did a steady 600' per minute decent..

A few minutes prior to that I seen a heavy crossing overhead at maybe 3500-4000' separation and was concerned with that but felt nothing.

Anyways we made it home and that's all that matters :)
 
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Pinstriper said:
On a flight from O22-OVE today while at 6,500' NorCal comes on and tells me an MD80 was gonna cross my path at 8,000' "caution wake turbulence".
I responded with I was going to decend to 4,500'.. All the while wondering when I was gonna be hit with anything. So my question is what would you have done? I assumed I took appropriate action and aside from mechanical turbulence we felt nothing.. I did a steady 600' per minute decent..

A few minutes prior to that I seen a heavy crossing overhead at maybe 3500-4000' separation and was concerned with that but felt nothing.

Anyways we made it home and that's all that matters :)
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I'm with you. Anytime ATC informs me of a conflict like traffic at my altitude or close to it and/or wake turbulence I will state my intentions of a climb or decent to avoid anything that could affect me.

like you, I just wanna make it home safely.
 
I probably would have pressed on at 6500 and started looking for the Mad Dog. 1500 below gives the vortices a lot of time to dissipate, and at that altitude, the jet was probably still moving pretty fast, which reduces the vortices, and the fact that it was crossing rather than same/opposite direction also dramatically reduces the problem.
 
Reasonable response, though a 1500' vertical separation would have been ok at cruise altitude (see AIM 7-3-4). Just be prepared for a possible pitch or roll excursion. Slow to maneuvering speed if you want to minimize any disruption.
 
You made the right call. I crossed paths once with a climbing 747 outta SFO. He was an easy 10-15 miles out and long gone and I though I was well above his climb path...wrong. It was like we hit a concrete wall and got slammed down hard with all of us and everything in the baggage compartment getting launched into the ceiling and serious headache the next day.
 
Shawn said:
got slammed down hard with all of us and everything in the baggage compartment getting launched into the ceiling and serious headache the next day.
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Yikes. Don't you and your passengers wear tight seatbelts?
 
Shawn said:
You made the right call. I crossed paths once with a climbing 747 outta SFO. He was an easy 10-15 miles out and long gone and I though I was well above his climb path...wrong. It was like we hit a concrete wall and got slammed down hard with all of us and everything in the baggage compartment getting launched into the ceiling and serious headache the next day.
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If that happened my wife woulda killed me if the vortices didn't !! Damn!!!
 
Whatever makes you comfortable,is the right decision.
 
IFR, even in CAVU, will generally keep you out of such situations.
 
I would have kept going and waited to see how close he was going to pass. 1,500 ft is a good distance. That's 500 ft greater than what would be provided for an IFR aircraft. Also, like Ron said it was crossing and not same direction so you have less exposure. I had an MD-80 cross 2 miles in front of me and 500 ft above the other day. I waited for a bump but got nothing.

Either way, you're PIC and it's your aircraft.
 
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Exact same altitude difference happens to me when I fly from POC to CRQ/SEE or anywhere in the San Diego area IFR. I'm at 7000 and the KAYOH arrival into SNA puts jetliners at 8200-8500 right over the top of me and I get a warning from ATC for "Caution Wake Turbulence"

Only felt it once - and it was just a little jiggle.

I would not have changed altitudes at all - those jetliners at 8000 are never dirty - gear is up, flaps miight be 1 or 2, maybe 5 degrees. and with the winglets now on so many of them, there is little downward wake coming off them. . . when over 180 knots.
 
Shawn said:
You made the right call. I crossed paths once with a climbing 747 outta SFO. He was an easy 10-15 miles out and long gone and I though I was well above his climb path...wrong. It was like we hit a concrete wall and got slammed down hard with all of us and everything in the baggage compartment getting launched into the ceiling and serious headache the next day.
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You sure that was the 747? 10-15 miles is more than 3 minutes. 747s do have nasty vortices, but that's a long time.

I've gotten slams like that off Montara Mt. with no other traffic in the area.
 
You done it right. My one experience with wake from a 737 that was miles away convinced me to not mess with it at all. Only time I ever had full aileron deflection and was still rotating the wrong way. No bueno.
 
I got plowed under near Dover by the wake of a C-5 or C-17 minutes after it passed. I avoid wakes after that tumble...

You lived and avoided it...you did well!
 
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acrophile said:
Yikes. Don't you and your passengers wear tight seatbelts?
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That is when I leaned my seatbelts do a good job of keeping me from going forward, NOT up!

Pinstriper said:
If that happened my wife woulda killed me if the vortices didn't !! Damn!!!
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Yeah, it left a mark

MAKG1 said:
You sure that was the 747? 10-15 miles is more than 3 minutes. 747s do have nasty vortices, but that's a long time.
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Without a doubt. It was actually "747 HEAVY" and the incident was when he was at EXACTLY my three o'clock and we passed his flight path. I too have had just little "wabbles" from other wake turbulances and didn't think much of it especially taking into account his distance and time that we crossed.

We learn of wake turbulence on takeoff and landings in school...that day I leaned about in enroute!

I did post about the experience a while back:

http://www.pilotsofamerica.com/forum/showthread.php?t=65289
 
Just the other week the final report came out for the PA28 that crashed into Lake Michigan after passing wake turbulence behind a Mad Dog (I think) at 1800ft. Pilot was a veteran CFI with over 30.000hrs. That said, at 6500ft I would probably have continued if terrain was low. But at low level it can be a killer.
 
Ron Levy said:
I probably would have pressed on at 6500 and started looking for the Mad Dog. 1500 below gives the vortices a lot of time to dissipate, and at that altitude, the jet was probably still moving pretty fast, which reduces the vortices, and the fact that it was crossing rather than same/opposite direction also dramatically reduces the problem.
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I'd agree. If I moved every time I had a traffic advisory, I'd never be able to stay on altitude.
 
Shawn said:
That is when I leaned my seatbelts do a good job of keeping me from going forward, NOT up!
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Unless the belt is defective, that shouldn't be possible if the belt is properly adjusted.

Rather than waiting for turbulence, everyone should test their belt adjustment as a checklist item before takeoff. Try wiggling forward or upward in your seat and if you can move significantly, the belt isn't tight enough. If you find that your head can reach the ceiling, you're at risk for serious injury or pilot incapacitation, so don't fly until the problem has been fixed.
 
A 747 that's heavy would be climbing at 250-260 knots. So he's doing a bit over 4 miles per minute. Therefore, it's quite possible.

MAKG1 said:
You sure that was the 747? 10-15 miles is more than 3 minutes. 747s do have nasty vortices, but that's a long time.

I've gotten slams like that off Montara Mt. with no other traffic in the area.
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Cpt_Kirk said:
I'd agree. If I moved every time I had a traffic advisory, I'd never be able to stay on altitude.
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Up where I'm at I never get these, but yesterday we were east of Sacramento international's flight path east bound traffic and it's the only time is been advised. Only other advisories had been whenever I flew into SMF and departing there..
My CFi buddy with 14,000 hrs flying heavies confirmed that it probably was flying pretty clean at that moment but since I could safely descend to 4,500 why not? Maybe I read forums to much and other peoples horror stories so I wasn't taking any chances lol!!
 
Pinstriper said:
My CFi buddy with 14,000 hrs flying heavies confirmed that it probably was flying pretty clean at that moment but since I could safely descend to 4,500 why not? Maybe I read forums to[o] much and other people[']s horror stories so I wasn't taking any chances lol!!
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Flying clean increases, rather than decreases, wake turbulence. Heavy, clean, and slow is the worst combination (see AIM 7-3-3-a).
 
Considering the profile the MD-80 is in, if it's clean with no lift producing generation (flaps) extended, then wake turbulence would be at it's greatest because of the wing's high angles of attack. But because it's in a cruise profile with a minimal angle attack (pure speculation that it's in a cruise profile that is) than the wing would be producing less wake turbulence than during an approach. Wake turbulence also descends and rapidly dissipates at up to 1,500 feet per minute (someone check me on that) but that's assuming the aircraft is at a high angle of attack. I'm not saying I have an answer or a solution here, simply some input. Without reference, I believe it is said the aircraft produces this turbulence until the nose gear touches down on the runway and the wing no longer has an angle of attack relationship. You are the Captain though my friend, and made the most conservative and safe decision. However, I would have maintained 6,500' given the conditions you described. Wake turbulence isn't a game, and anytime tower warns you of it and you accept a landing clearance, you've just assumed full responsibility if there's an accident. I.e. I understand it's a different scenario but to just to share with our community.. a Mooney being warned of a landing Gulfstream's wake turbulence 2 minutes ahead of him, the pilot accepted the landing clearance despite the warning and he ended up being flipped over while in ground effect. Thank the Lord, he and his wife survived. It happened right in front of me. It makes me think twice every time I hear that caution by ATC.
 
Thanks for all the replies as a low time pilot 170hrs I turn here to ask a few questions and get good answers..
 
What would you do as your taxiing to the ramp and ground says, "Be advised that commuter jet (you're crossing behind) will be starting engines."

All I did was slow down, bank the ailerons in that direction, and pray.
 
DrMack said:
IFR, even in CAVU, will generally keep you out of such situations.
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I got slammed pretty hard once while flying IFR when a C130 crossed my path with 1000 ft of vertical separation. The only evasive maneuver guaranteed to avoid the wake would be to climb to the crossing aircraft's altitude and fly behind it (with appropriate lateral separation). My standard reaction these days to such a situation is to slow to turbulence penetration speed prior to crossing the heavy's path.
 
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