Enroute Holding

[ThunderSkye]

What appeared to be a simple request has turned into a serious discussion, can anyone clarrify.

The other day when approaching Chicago (ORD) we were given holding instructions due to congestion, and they were as follows

“Hold North on the 360 Radial from MSN at FL210, 15 NM legs approved, and own speed”

My question is, does this mean that the inbound leg can be up to 15NM, or does it mean that an inbound turn must be commenced at 15NM from MSN when on the outbound leg?

Bear in mind that at 280 KTS after turning outbound and abeam MSN outbound we were at 9NM already

[barit1]

Would it help to ask the ATC ladies & gents? My bet is you'd get a variety of answers.

If holding at "own speed" then the turn radius is a variable quantity - is that what they meant?

[ThunderSkye]

I don't think so as the speed was our request, I am looking for clarity on the 15nm, if it is the leg distance as given, or is it as depicted in the jepp atc section which shows a turn at 15 dme

[Jetavia]

I would think you should hold as they say .. north of MSN on the 360-R using 15 nm legs at your own speed.. meaning you should start your turn at 15 nm on your outbound leg and can use the speed of your liking.

ICAO DOC 8168

1.3.5 Outbound leg length based on a DME distance

If the outbound leg length is based on a DME distance, then the outbound leg terminates as soon as the limiting DME distance is reached.

http://dcaa.slv.dk:8000/icaodocs/Doc%208168/8168_v1.pdf

[The Real Slim Shady]

Interesting.

I would have said that putting a 15nm leg in to the computer would have resulted in the outbound commencing from wings level i.e at completion of the turn, and terminating 15nms later.

[ThunderSkye]

Jetavia, as a matter of interest in the USA timing is based on the inbound leg and not the outbound as the rest of the world. However as I see it normally a leg distance can be given, or requested to avoid all the turning of a standard holding pattern which would be 1.5 minutes at FL250.
In this case if we had turned inbound at 15nm, our outbound leg would have been only 46sec with the prevailling winds. This is more restrictive than the standard 1.5 min, and I don't think this was the intention of ATC.
However I may be misinterperiting the request

[Jetavia]

Thunder .. maybe the answer to your Q can be found in the US AIM http://www.faa.gov/ATpubs/AIM/Chap5/aim0503.html#5-3-7

[westhawk]

ThunderSkye,

It appears that the answer is in fact contained within the AIM. (thanks, Jetavia) It looks like when you are flying the hold by reference to DME or RNAV, as in a defined leg-length hold, it is the outbound leg that is measured and defines the point where the inbound turn is commenced. Only on timed holds is the length (elapsed time) of the outbound leg adjusted so as to cause the inbound leg to last the appropriate length of time.

Thanks for sharing this one, Thunder. Since I have a trip to Chi-town later this week, it probably means I'll get assigned a hold too! At least I've now had a refresher on what to do when I get it. Thanks, buddy!

Best regards,

Westhawk

[scanscanscan]

Enroute high altitude holds......consider your speed.....slowing up in a heavy L1011 to hold enroute not followed by a descent resulted in not being able to accelerate to cruise speed in level flight with MCT set for one of our crews.
Skyhawk...If confused in future by such clearences....We would suggest you ask ATC to..."Say again "fully"xxx ATC hold instructions"
This revealed one sim instructor who had no knowledge of how he should issue correctly and in the correct sequence an ATC hold instruction. He was alwys confuseing his crews under check in exactly the same way as you were.

[hawk37]

Scan,

I question why your L1011 crew would have had difficulty accelerating from holding speed. Seeing as the intent of holding speed is to provide the least fuel flow, while still allowing enough of a margin for control and pilot technique issues, this also means minimum drag speed, or close to it. Ergo, minimum thrust required, and therefore near the maximum excess thrust available. So holding speed should give you very close to the best acceleration possible once you decide to resume cruise.

Hawk

[scanscanscan]

The manual after this incident now says minimum holding speed at high altitude (possibly means optimin altitude for weight) for the L1011 is LRC unless immediately followed by a descent.
Hopefully 411A can comment and set the record straight.

[411A]

Scanscanscan is spot on.
Minimum holding speed at high altitude in the Lockheed tri-motor is indeed LRC.
As the L10 has a true high-speed laminar flow wing, any slower is just asking for trouble, especially in -22B powered models.

I was once asked by London control to hold at 210KIAS at FL370.

Quite frankly, they really had positively no idea about jet transport aircraft performance at higher altitudes...then.
I wonder if it has improved?:}

[punkalouver]

No timing required during a DME hold.