View Full Version : When to start a turn
Hi all,
What methods are in use to calculate when to start a turn when flying towards an NDB to join the hold, so you don't overshoot or undershoot the qdm or qdr?
Thanks for the comment.;)
Tinstaafl
17th Oct 2004, 23:06
Start the turn after positive indication of station passage.
Old Smokey
17th Oct 2004, 23:44
Follow Tinstaafl's advice. PANS-OPS procedures are developed for initiating the holding pattern entry after station passage. The lateral protection from obstacles assumes that you do so (as long as you follow all of the other requirements correctly.
It's just that the picture i saw of a holding pattern i made with a B737 simulator looked weird. I wanted to hold on the 090 inbound to the NDB, left hand turns, and i was heading north on the 180 inbound. This would be a direct entry. So i made a turn over left after station passage to heading 090 and the picture showed a balloon on the right hand top side of the holding pattern.
A little correction:
I made a parallel entry with a turn over right towards heading 090 after station passage.
OzExpat
18th Oct 2004, 07:51
The "parallel entry" has me a bit tossed, but... If inbound 180 to the holding pattern you described, I'd make a direct entry so, when I see positive indication of station passage, I'd turn left onto 270 to join the outbound leg. This manoeuvre will produce a somewhat irregular looking track and may result in a slight overshoot of the inbound track, in the turn from the outbound to the inbound.
Pans Ops protection areas account for this, provided that you don't exceed applicable airspeed and bank angle limitations.
The chances are also pretty good that, if you'd gone right around the pattern once or twice, after completion of the sector entry, the plot of your track might still look a bit irregular. This can occur because of over-estimation, or under-estimation, of drift. The protection area makes an allowance for this because of the lack of track guidance on the outbound leg of the pattern.
square leg
18th Oct 2004, 08:09
Once you pass the station (overhead it) carry on flying for 15 seconds and then turn left on 270 +/- WIND correction for the remaining 45 seconds and then left again towards the station, a so-called "special-direct-entry".
Thanx guys (and girls?)
The picture i saw after the session got me confused. That's why i thought that there might be a way to start the turn earlier in stead of overshoot. But i guess with NDB holdings the only way is to overshoot because you need to pass the station first?
Tinstaafl
18th Oct 2004, 13:47
Yes. Your only known position is at the time you cross the aid. The rest of the time is either DR for a limited period or intercepting a radial bearing. Flying over the aid has the effect of resetting any cumulative error to zero on each pass around the hold.
SMJP - the way you have described the hold means a parallel entry is correct in PANS OPS. You will therefore get your little 'balloon'. You CANNOT anticipate the turn for an NDB hold because you require station passage to confirm position. I think an IMMEDIATE turn is more correct after station passage in this case?
Keygrip
18th Oct 2004, 17:27
I think I'm with BOAC - the way I READ I(passed tense, pronounced RED it) - the phrase 180 inbound was meant as travelling from South to North - so the phrase 090 inbound could be flying from East to West - which would make a right, parallel, entry at the beacon.
Wouldn't it?
Just goes to show - a picture paints a thousand words.
Keygrip, you're right. With 180 inbound i meant south to north and 090 inbound was east to west. Strange, flew lots of holdings but the first time i noticed the strange balloon. :O But thanks to your comment, guys, i know it's allright. :ok:
Old Smokey
19th Oct 2004, 04:52
I find it a bit worrying reading here and there throughout this thread about 'personal adjustments', 15 seconds here, 45 seconds 'special entry' there, and so on. I've spent (too many) thousands of hours in the instructor's chair in the simulator watching students re-draw the Jeppesen diagrams on the monitor over my head. Many of these 'personal adjustments' take them right outside the protected area.
On 99.9% of occasions you'll live to tell the tale, but there are some stinkers out there with very solid obstacles sitting right on the edge of the PANS-OPS protected area.
OzExpat
19th Oct 2004, 06:53
Re-reading our friend's second post, it's clear that he was heading north toward the NDB (ie 360 inbound, or inbound on the 180 radial if you like). That makes it a left turn direct entry to the pattern. I may have confused the issue a bit in my post, by referring to "180 inbound", but I still stand by my comment about the need for a direct entry in this instance.
Any other type of entry would, in my view, not be legitimate. And it might not be contained within the holding pattern's protection area. Begins to look like it might be good idea for our friend to repeat that particular sim session.
keithl
19th Oct 2004, 08:50
The actual interpretation of SMJP's post has been well covered by others, but I'm prompted to ask, "Why is he asking us? Doesn't the Sim Instructor debrief this stuff?" I certainly would.
Thanks Old Smokey and OzExpat.
Did you actually have to make such a holding entry in real live? I mean a holding where such a 90 degree turn over right for this parallel entry was necesarry? (according to PANS OPS even 110 degree maximum for parallel entries) Because such a parallel entry can put you way out on the other side of the holding side and maybe outside the protected area.
SMJP - the WHOLE of the entry manouevring area is 'protected' as well as the hold itself as long as you do not sail happily on too far past the beacon or enter at too high a speed.
180 degree Turn to Join a Formation
Was once on the flight deck of a KC-135 tanker with 4 others mothering some F111s NW bound from Australia towards Guam. Another 4 tankers launched out of Guam to provide further refuelling support.
Radar showed both formations approaching each other on reciprocal headings but with about 10 miles offset.
The objective was for the SE bound tankers to execute cross over turns to join the NW bound tankers in wide line abreast.
The lead navigator must have been a wizz. I heard his count down to start the turn to a reciprocal.
After what seemed about 10 minutes those 4 tankers had turned through 180 degrees and ended up almost perfectly spaced line abreast.
The accuracy of that manoeuvering seemed to be phenominal to a non tanking pilot.
Perhaps there are some tanker crews out there who can describe how you do it.
Tinstaafl
19th Oct 2004, 15:18
SMJP, maybe ou're missing the point? The parallel sector entry, including the airspace that you'll use after crossing the aid is designed as part of the hold entry procedure.
I think your concerns are incorrectly creating a problem where none exists provided you conform to the procedure.
blody tipos
Milt - old hat to a Lightning driver:D I just wish the brain cell could remember the way we set up a 180 and the range at which we turned in to achieve a 2 mile slot for missiles. I even got it to work sometimes:D The really difficult one was to roll-out ahead of a tanker:D :D
Had to do it on a tanker for a 1/2 mile slot once when I was just a wee bit short of juice at 0300 over a winter North Sea - luckily that worked 'cos I had NO spare.
Surely a WWOL will come past here and give you the geometry. Any QWIs on freq?
Tinstaafl, you're right.
My concerns are indeed incorrectly creating a problem. As BOAC and most of you said: as long as i stick to the procedures i should be within protected space.
And keithl, i'm sorry i didn't notice your response. I was flying the sim on my own, without instructor, just to prepare for gradings when i noticed this. That's why i posted the question.
Thanks once again for the help guys.
OzExpat
20th Oct 2004, 07:38
SMJP
Did you actually have to make such a holding entry in real live?
I design IFR procedures and also fly them. I've had occasion to have to make a turn of up to 105 degrees, but never 110 degrees. The rules here state that, if within 5 degrees of a sector entry boundary, we can use either of those sector entries. So, when I'm in that situation, I always use the one that produces the smaller heading change.
And, before anyone asks, yes, the sector entry protection extends to that 5 degree zone of flexibility at the boundaries.