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Proper procedure for timing racetracks


fmedges

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It's just a holding pattern with a time to exit. Don't really need math if it's what I'm thinking. Besides, IIRC, the legs are distance, not time.

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I’m about the ramp up my case 3 training and I was wondering how I am going to time my racetrack pattern in the Marshall stack. What math do I need to do to figure out my timing between the 4 racetrack points?

 

I hope someone who's been there /done that will answer... otherwise:book:

NATOPS says 6 min pattern but from what I understand: the turns are 2min. and the legs anywhere from 1 to 2 min each... depending on your expected approach time. For instance, if you just passed your fix, started your outbound turn and your EAT is coming up in 4 min. you will simply make a 360 turn or possibly even tighten up the turn to arrive at the fix within 10 sec. of your push time.


Edited by Gripes323
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I presume turns are standard rate so a 180 will take 1 minutes and each leg will be 2. Too arrive on time just shorten or extend the outbound leg. With wind it gets a little more complicated.

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I’m about the ramp up my case 3 training and I was wondering how I am going to time my racetrack pattern in the Marshall stack. What math do I need to do to figure out my timing between the 4 racetrack points?

 

 

 

 

Wags has a vid up showing everything. Follow his steps and should be ok.

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Standard rate turn is 3 degrees per second, so a 180 degree turn is always 1 minute at standard rate.

This works at any speed, higher speeds just make for a larger lateral piece of airspace required for your pattern.

If your aircraft can show your track above ground, it’s easy to compensate for wind drift, just fly the headings required to give your correct inbound and outbound tracks.

If not, you have to calculate your wind correction angle (WCA) that gives you the required heading for the inbound track towards your holding fix. On the outbound leg, you take that inbound WCA times 3 to compensate for the outbound leg plus wind’s influences on the two 180 degree turns (width of turns).

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Practical pilots are not transfixed by standard rate turns and don’t vary bank angle to achieve standard rate turns. The SOP is you fly a standard bank angle .... and in reality don’t ever look at the turn needle :) The usual method to adjust hold time is vary the straight leg time but even better method is TLAR.

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Yes, standard rate turns at high speeds require too much of an angle of bank.

For the marshal pattern, NATOPS says 6 mins standard. CNATRA CV Procedures publication says 2-minute turns and 1 minute legs are normally use, but the primary goal is to depart at the expected time (within 10 seconds), so adjust your patterns accordingly. An older version also said to keep pattern duration between 4 and 8 minutes.

 

Ex: you have en EAT (Expected Approach Time) of 0350, and arriving on your marshal fix you see it's 0339, meaning you've got to depart in 11 minutes ; you can choose to do one 6-minute pattern then one 5-minute pattern to arrive on time.

 

Personally, I have taken to using a timer or watch, it is quite simple: start your first turn, start timer (or check your watch). Fly your 180 turn and your outbound leg. When the timer reaches half the total desired time for the pattern, turn inbound. Try to be consistent in your flying for the whole pattern. It works really well. And I can simply use 30° AoB turns all the time, and my wingmen are happy :)

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I just fly the "wiggly" pattern approach until it all looks about right. Then I land.

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I do not know what is the term "precog" but turn rate given velocity is function of radial G which uniquely describes a bank angle if the turn must be level. Rate-one turns in fast jets often require quite high G so half-rate turns are used instead. 250KCAS is about 300 KTAS at 10kft. That's a 39.5° bank at 1.29g for SR. That's not exceptionally high but more than 30 bank is rarely prescribed. The 180 knot figure corresponds to a 25 bank which is the typical limit of what an airliner is expected to do.

 

To time departure from a hold you recognize your hold pattern duration (e.g. 4 minutes) and remove all the whole number laps that you can and examine the remainder. If it's less than the time to do two turns with zero straight leg (e.g. 2 minutes) then add back a whole lap's duration to the remainder. Your remainder should be between 2 and 6 minutes for a 4-minute lap pattern.

 

Then you try to do this "weird lap" as early as possible leaving standard laps later. If your time to hold is 13:30 then you want to do a 5:30 lap and two 4:00 laps. If your time to hold is 10:30 then do a 2:30 lap and two 4:00s. The turns are done as usual but the straight legs are the lap time, minus the turn times, divided in half. With standard turns your legs are 60+75 seconds for a 5:30 lap and 15 seconds for a 2:30 lap.

 

But of course you have to be careful that a fat lap doesn't leave your designated holding area. If they want you between DME 25-30 for straight legs then the total size is probably within DMS 22-33 including the turn radii. In any case 300 knots for a minute is 5nm. Your longest straight flight segment can't be longer than 1 minute and stay inside those DME numbers. If limits allow (and they probably do) you're probably permitted 90 second legs especially at high altitudes. No one cares if you turn within tighter limits. You are perfectly welcome to fly continuous circles if you want.

 

But we're not doing SRT, but 30 degrees bank with some time spent rolling in and out. That's about 2 degrees per second or rate two-thirds giving 90 second turns. True two-thirds rate bank is 28.8 so this will work fine. So 60 second legs with 90 second turns makes a 5 minute pattern, nice round numbers.

 

Let's apply this to a more real example. Your push time is given 13:20:00 and you show up and cross the initial hold fix at 12:57:21. You have 22 minutes and 39 seconds to hold. That could be 8 fives and a 2:39.. hmm, too short. How about 7 fives and a 7:39? Too long. We need our odd ball in the 3-5 minute length. How about shorten the first lap to 30 second legs both ways to shave a minute off? That will add a minute to the odd ball bringing him from 2:39 to 3:39 and we can do that. And if we might as well do the weird one first so the mental math gets easier.

 

Plan is:

Time 12:57:21

3:39 (90+19.5+90+19.5)

Time 13:01:00

4:00 (90+30+90+30)

Time 13:05:00

5:00

Time 13:10:00

5:00

Time 13:15:00

5:00

Time 13:20:00

 

Of course you won't be perfectly precise so take note of how far off you are from on schedule and add/subtract half of that from the straight legs. There is also wind to consider. If the return legs have headwind and you show up 11 seconds late then make the next outbound 11 seconds shorter (to get that 11 back) and all subsequent outbound legs half of 11 shorter (to prevent losing it again).

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It's just a holding pattern with a time to exit. Don't really need math if it's what I'm thinking. Besides, IIRC, the legs are distance, not time.

 

 

 

 

Listen to this video:

 

 

You'll realise fast that if you're 280 degrees away from your exit when it's your turn to descent, you'll skrew the guy on top of you and skrewing up the interrval on deck... i think. As all pof them have a time schedule, so if you don't plan your exit when it's the time and far from it, the stacks goes down the drian because of you.

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If you know better way to exit holding pattern via holding fix accurately to second, you can share that with us.

 

 

Before I get started, dont' take this as being rude. If you're doing timed legs and you have to be out at the top of the hour and you're two min into your outbound leg and you have 4 min til exit, it's time to turn. It's really simple. You're doing timed legs, you can see a clock, just some common sense and basic math. There's no need for complication. You don't have to complete an entire leg/racetrack to exit a hold. Just turn when you need to and exit at the hold point.

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Listen to this video:

 

 

You'll realise fast that if you're 280 degrees away from your exit when it's your turn to descent, you'll skrew the guy on top of you and skrewing up the interrval on deck... i think. As all pof them have a time schedule, so if you don't plan your exit when it's the time and far from it, the stacks goes down the drian because of you.

 

 

Yup, I forgot they're timed, either way, it doesn't really make much of a difference. In fact, being timed legs, it simplifies things.

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I don't think it's rude, I just think you underestimate the task. :)

 

I've yet to find official information for AET time tolerance.

 

If it's inside assigned minute, it's really not a big deal. I believe that's not case because that would allow two aircraft to exit with only one second separation.

 

If it's +-15 sec it's not a big deal.

 

If it's +-5 sec it starts to be a problem - you have to plan carefully for that.

 

If you need to hit exact second on exact mile, that's too much workload. That requires too much attention in busy airspace.

 

 

It's even more important in game where we do not have ATC to coordinate traffic.

 

From what I've heard it's down to the second and maybe as big as +/- 5. Any deviation in time screws up the spacing between planes and thus the recovery on deck.

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We are in fighter planes. In real life do the pilots have to maintain standard turns like airliners have to do or can they add some power and g's and tighten it up alot to better time the exit from the stack?

 

I believe that they can do what they want as long as they are on time and at the correct place for exit. The standard or half standard rate turns just make the timing easier to calculate.

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Timing procedure I use:

- check time-over-holding-fix when you start your outbound turn (or start an elapsed-time-counter)

- monitor the elapsed time you needed for your 180-turn (TTurn)

 

- as soon as out of the 180: check time-remaining-until-your-expected approach time (Tremaining)

- calc: Tremaining-Tturn=T2legs | T2legs : 2 = T1leg

- fly the outbound leg for the time you calculated (T1leg), then start your inbound turn

 

 

In other words:

- check what time you need for the first turn (to know how much time you will need for the second turn)

- check how much remaining time you have after that first turn until you have to be at the holding fix

- substract the time you will need for the 2nd turn from the remaining time you have to get the available time you have for both legs (outbound and inbound) and divide that by 2 to get the time you have to fly on the outbound leg

 

Edit: Use minor speed corrections on the inbound leg to compensate wind and moving-away ship, maybe start the inbound turn just a a few seconds (5-10 seconds) earlier to compensate for the moving-away ship (during a 3 minutes flight time it moves approx. 1 NM away given a boat speed of 20 kts)


Edited by -Painter-

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I don't think it's rude, I just think you underestimate the task. :)

 

I've yet to find official information for AET time tolerance.

 

If it's inside assigned minute, it's really not a big deal. I believe that's not case because that would allow two aircraft to exit with only one second separation.

 

If it's +-15 sec it's not a big deal.

 

If it's +-5 sec it starts to be a problem - you have to plan carefully for that.

 

If you need to hit exact second on exact mile, that's too much workload. That requires too much attention in busy airspace.

 

 

It's even more important in game where we do not have ATC to coordinate traffic.

 

 

I don't think I underestimate it, I just don't think it's all that complicated as long as you're staying on top of where you are and when you have to leave. I've done it many times either in holds or passing over a drop point to drop skydivers for SOCOM demos. In all honesty, it's nearly eyeballing it and I've done it to the second.

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I just read through this myself because I've been looking at the Case I and Case II/III holding patterns. CV OPS manual for the T-45 says that 6-minute patterns are standard: 2-minute turns and 1-minute legs. Performed at either max conserve fuel flow or NATOPS holding speed. CV NATOPS says holding speed is according to individual aircraft NATOPS. The Hornet's NFM-000 NATOPS only gives 220-240kts between 15,000 and 20,000 feet. And I'm guessing the max conserve fuel flow is something that needs to be calculated from the NFM-200 charts.

 

So problem number one is: What speed should we be flying the patterns at?

 

And problem number two is: How do we find out our AoB to make a 2-minute turn at whatever that speed will be...preferably without breaking out a Ti-84.

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