DME teardrop holds
Thread Starter
Join Date: Sep 2014
Location: deer
Posts: 18
Likes: 0
Received 0 Likes
on
0 Posts
DME teardrop holds
Hello,
i am studying for my FAA CFI-I and have a question about DME teardrop holds.
If the hold i am doing has 1 NM legs, i fly to the fix, fly 30 degrees in the opposite direction ton the hold for 1 NM and then turn SRT inbound, that im OK with.
If the hold leg lengths are 6nm for example, i have been told you fly that first 30 degrees also for 6 miles and then turn inbound. The trouble is, if you turned inbound at SRT you would be nowhere near the inbound course.
What is the correct procedure???
thanks
i am studying for my FAA CFI-I and have a question about DME teardrop holds.
If the hold i am doing has 1 NM legs, i fly to the fix, fly 30 degrees in the opposite direction ton the hold for 1 NM and then turn SRT inbound, that im OK with.
If the hold leg lengths are 6nm for example, i have been told you fly that first 30 degrees also for 6 miles and then turn inbound. The trouble is, if you turned inbound at SRT you would be nowhere near the inbound course.
What is the correct procedure???
thanks
Join Date: Jan 2005
Location: Hotel this week, hotel next week, home whenever...
Posts: 1,492
Likes: 0
Received 0 Likes
on
0 Posts
I was taught and teach not to teardrop a DME hold as once away from the fix you don’t have positive tracking - possibly stems from non RNAV capability when I was a lad! One of our instructors did say it was in the ICAO docs somewhere...I’ll ask him about it again.
However, you’re correct in that the full 30 offset for the whole time or distance would make regaining the inbound track impossible in one smooth turn.
However, you’re correct in that the full 30 offset for the whole time or distance would make regaining the inbound track impossible in one smooth turn.
First of all:
You’ve got a choice depending on the hold
Light aircraft you wouldn’t fly 6 mile legs but a timed hold.
But for the sake of the discussion, entry’s are at pilots discretion.
There is no ‘wrong’ entry, just a more correct or more convenient one.
So when the hold is 6 mile legs this means the inbound course is 6NM.
This doesn’t include the entry.
So you fly the 1 min entry prior to turning, cross the fix then turn and fly 6NM outbound +/- wind correction.
You’ve got a choice depending on the hold
Light aircraft you wouldn’t fly 6 mile legs but a timed hold.
But for the sake of the discussion, entry’s are at pilots discretion.
There is no ‘wrong’ entry, just a more correct or more convenient one.
So when the hold is 6 mile legs this means the inbound course is 6NM.
This doesn’t include the entry.
So you fly the 1 min entry prior to turning, cross the fix then turn and fly 6NM outbound +/- wind correction.
Thread Starter
Join Date: Sep 2014
Location: deer
Posts: 18
Likes: 0
Received 0 Likes
on
0 Posts
Ok, lets use the top example of the pictures, the OM hold. so im using that has a hold in lieu of a PT, and the leg lengths a 1nm.
I fly outbound r/w heading (say a heading of 270) and reach the OM . i turn to heading of 240 and fly that for 1 nm and then start a SRT to the right to fly back inbound.
Say, for example, the leg lengths are now 6 nm. I fly 270 to the fix, then fly 240 do i fly this portion 6nm? that is what is confusing me?
I fly outbound r/w heading (say a heading of 270) and reach the OM . i turn to heading of 240 and fly that for 1 nm and then start a SRT to the right to fly back inbound.
Say, for example, the leg lengths are now 6 nm. I fly 270 to the fix, then fly 240 do i fly this portion 6nm? that is what is confusing me?
Couple of points:
First, under TERPS, holding airspace is weighted towards the holding side. There’s more protected airspace on the hold than on the non-holding side.
Second, the objective of the entry maneuver is to put the plane in a position to intercept and track the inbound course as simply and expeditiously as possible. Doing so ensures track guidance to remain within holding airspace.
Given the above, the point of the entry is to put the plane in a position to do a SRT from teardrop to the inbound course. The 1:60 rule says 1 degree subtends 1nm at 60 nautical miles. As the turn diameter of a plane holding at 100 KTAS is approximately 1 nm (the computed turn radius is 0.53 nm, double it for diameter), the pilot needs to be 1 nm offset from the inbound course to accomplish the turn to intercept. One nautical mile at a distance of 6 nms from the fix is 10 degrees. No wind: fly the teardrop offset at 10 degrees (260*, in your example) for 6 nautical miles to make a SRT onto the holding course. If the DME hold was at the VOR, you could dial in the outbound corse for guidance, then reset the inbound course at 6 DME and start the turn.
Given the 16* angle of bank at 100 KTAS for a SRT, there should be margin for some overshooting wind on the turn.
GF
First, under TERPS, holding airspace is weighted towards the holding side. There’s more protected airspace on the hold than on the non-holding side.
Second, the objective of the entry maneuver is to put the plane in a position to intercept and track the inbound course as simply and expeditiously as possible. Doing so ensures track guidance to remain within holding airspace.
Given the above, the point of the entry is to put the plane in a position to do a SRT from teardrop to the inbound course. The 1:60 rule says 1 degree subtends 1nm at 60 nautical miles. As the turn diameter of a plane holding at 100 KTAS is approximately 1 nm (the computed turn radius is 0.53 nm, double it for diameter), the pilot needs to be 1 nm offset from the inbound course to accomplish the turn to intercept. One nautical mile at a distance of 6 nms from the fix is 10 degrees. No wind: fly the teardrop offset at 10 degrees (260*, in your example) for 6 nautical miles to make a SRT onto the holding course. If the DME hold was at the VOR, you could dial in the outbound corse for guidance, then reset the inbound course at 6 DME and start the turn.
Given the 16* angle of bank at 100 KTAS for a SRT, there should be margin for some overshooting wind on the turn.
GF
The examiner will frown upon anything which does not have a reference such as the FAR-AIM or the FAA Instrument flying handbook.
http://www.faraim.org/aim/aim-4-03-14-320.html
Fly one minute outbound.
http://www.faraim.org/aim/aim-4-03-14-320.html
Fly one minute outbound.
Thread Starter
Join Date: Sep 2014
Location: deer
Posts: 18
Likes: 0
Received 0 Likes
on
0 Posts
Thanks for the insights into this.
B2N2, AIM does say fly 1 minute outbound but it then goes on to say..
DME/GPS holding is subject to the same entry and holding procedures except that distances (nautical miles) are used in lieu of time values...
So i read that to mean, if you would normally fly the 30 degree entry for one minute, in a DME hold this becomes 1 nm.
There is nothing in the AIM, that i can find, that mentions the entry into a teardrop hold immediately after flying over the fix changes (time or distance) in regard to the length of the legs.
B2N2, AIM does say fly 1 minute outbound but it then goes on to say..
DME/GPS holding is subject to the same entry and holding procedures except that distances (nautical miles) are used in lieu of time values...
So i read that to mean, if you would normally fly the 30 degree entry for one minute, in a DME hold this becomes 1 nm.
There is nothing in the AIM, that i can find, that mentions the entry into a teardrop hold immediately after flying over the fix changes (time or distance) in regard to the length of the legs.
No, it remains ONE MINUTE, just turn inbound prior to being 6 miles from the fix. The entry is not the same as the legs.
Using the one minute recommendation puts the plane holding at 100 knots turning 30* on the teardrop about 1.3 nm offset from the holding course and at 2.6 mike from the fix. Close enough for the turn inbound, but don’t be shocked if you need to “play” the turn to roll out on the inbound or even stop the turn to intercept before the fix. Being aware of the geometry is not unimportant.
GF
Using the one minute recommendation puts the plane holding at 100 knots turning 30* on the teardrop about 1.3 nm offset from the holding course and at 2.6 mike from the fix. Close enough for the turn inbound, but don’t be shocked if you need to “play” the turn to roll out on the inbound or even stop the turn to intercept before the fix. Being aware of the geometry is not unimportant.
GF
It’s hard to explain this without a whiteboard and a marker.
So the fix is 10DME and the inbound leg is towards the VOR.
( see previous picture)
As you track the radial outbound you notice you need 5 degrees wind correction to the holding side.
This is also the direction of the turn required for the Teardrop entry.
Distances in a DME hold do not apply to the entry.
Unless you’re flying a parallel entry in which case it’s easier just to truck along to the 6 miles.
So 30 degrees won’t be enough.
Triple your wind correction and add it.
So fly a heading which is 45 degrees.
If you’ve experienced a headwind while tracking outbound then extend past one minute.
Let’s say TAS is 120 and GS is 90.
Extend by 20 seconds as the difference in speed is 1/3 GS
If your windcorrection while tracking the radial to the holding fix is away from the holding side still use the 30 degrees as the wind is pushing you towards the safe ( holding side).
So the fix is 10DME and the inbound leg is towards the VOR.
( see previous picture)
As you track the radial outbound you notice you need 5 degrees wind correction to the holding side.
This is also the direction of the turn required for the Teardrop entry.
Distances in a DME hold do not apply to the entry.
Unless you’re flying a parallel entry in which case it’s easier just to truck along to the 6 miles.
So 30 degrees won’t be enough.
Triple your wind correction and add it.
So fly a heading which is 45 degrees.
If you’ve experienced a headwind while tracking outbound then extend past one minute.
Let’s say TAS is 120 and GS is 90.
Extend by 20 seconds as the difference in speed is 1/3 GS
If your windcorrection while tracking the radial to the holding fix is away from the holding side still use the 30 degrees as the wind is pushing you towards the safe ( holding side).
