I've heard many articles about crosswind correction in VOR holding pattern. They mainly tell the outbound leg=correction times three things for slow speed aircraft. I notice all of them require wind information in holding pattern. What if somehow under some circumstances the pilot doesn't have the wind information whatsoever in holding pattern? Like the wind may change unexpectedly. Is there any method to maintain precise 4 minutes holding pattern in such condition?
One you are established inbound on the VOR radial note the heading you are flying to maintain that course. The difference between that and the radial is your wind correction angle. Multiply it by 3 and apply it to the outbound course heading.
To do this you don't need to know anything about the wind. You just need to be able to intercept and track the inbound radial.
You can repeat this every inbound leg so if the winds are changing you can update your correction every 4 minutes and you always know you are on course one of ever four minutes. With the generous obstacle protection area even small errors will not compromise safety.
When holding, it is true that you should take then inbound wind correction and multiply it by three and use that for the outbound correction.
Your question centers on what happens if you don't know the correct wind information and obstacle clearance. Fortunately for us, the FAA has given us a wide obstacle clearance area for the holds. While it is important to stay on the protected side of the hold, if you find yourself on the unprotected side of the hold, you are still "protected".
Picture taken from http://forums.jetcareers.com/threads/holding-pattern-protected-area.80377/
The idea is to fly the correct entry procedure and it will help to ensure you stay within the obstacle clearance protected area.
- A direct entry requires passing the holding point and immediately turning to the outbound leg. You may not know the wind correction so fly the outbound heading. Upon turning inbound get back onto your inbound course and try to determine your wind correction angle
- A parallel entry requires passing the holding point and tracking outbound on the radial. You should be able to figure out your wind correction. Turn 180° + 45° to re-intercept the inbound course. At this point, you should have a good idea where the wind is coming from.
- A teardrop entry requires passing the holding point and turning 30° into the protected side. When you turn inbound, there should be enough time to figure out what the winds are doing.
If the winds are constantly changing, do your best to stay on the protected side of the hold, if you venture a little to the unprotected side, you are still covered.
For lateral corrections, use a trial an error process of crabbing to maintain the selected track to the fix. One the airplane maintains a stable track on the inbound leg, note the crab angle and make use of that, applying the same angle inbound to the fix and an the same angle in the opposite direction on the outbound leg.
To compensate for unknown headwinds and tailwinds, fly a consistent indicated airspeed and time your outbound leg from and inbound leg to the fix. Note the difference between intended and actual times to fly the leg eg you’re flying a 1 minute leg but it takes you 1 minute and 40 seconds from rollout on inbound leg to crossing the fix, there’s a 40 second difference. If your leg takes longer than planned at constant airspeed you have a headwind, if it’s shorter, you have a tailwind. Take half that difference and subtract that time for your outbound leg for inbound headwinds and add for inbound tailwinds. Eg as in the example above, difference was 40 seconds longer, so it’s a headwind. Half of that is 20 seconds so you should fly an 1 min - 20 seconds = 40 seconds long outbound leg so your next inbound leg is one minute long.