Teardrop Procedure Turn as a Course Reversal
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From: USA
For those seeking references, a wonderful book by Olle Åkerlind and Håkan Örtlund, Instrument Flight Procedures and Aircraft Performance provides explanations and illustrations of PANS-OPS as well as TERPS procedures.
Earlier versions of the book (titled From Takeoff to Landing) were at one time supplied by Honeywell at various aviation meetings.
Earlier versions of the book (titled From Takeoff to Landing) were at one time supplied by Honeywell at various aviation meetings.
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From: london, UK
you could do a bit of maths if you wanted to.
the radius of the base turn is 2.1 miles (10*asin(12))
you can use tan(bank angle)=TAS^2/(11.29*radius of turn in feet)
still wind, no slip, 160 kts gives me a bank angle of 10 degrees.
But you'd never bother to work that out. Use a hold entry or go outbound as appropriate and just use a rate one turn for the base and roll out on a sensible intercept heading (or just use the top of the course bar and then follow it in to intercept).
At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less (plate only gives time and descent rate for up to 160) so a rate one will keep you from going through the localiser (still wind)
Just a guess though, don't really know what I'm on about, not for operational use, caveat emptor and all that.
Its not a procedure turn by the way - a procedure turn is a way to reverse your course and hopefully come out on the reciprocal of the inbound track. The common one's are an 80/260 or a 45/180 with a one minute outbound leg. The immelmann is less common in IFR flying but you might get points for originality.
the radius of the base turn is 2.1 miles (10*asin(12))
you can use tan(bank angle)=TAS^2/(11.29*radius of turn in feet)
still wind, no slip, 160 kts gives me a bank angle of 10 degrees.
But you'd never bother to work that out. Use a hold entry or go outbound as appropriate and just use a rate one turn for the base and roll out on a sensible intercept heading (or just use the top of the course bar and then follow it in to intercept).
At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less (plate only gives time and descent rate for up to 160) so a rate one will keep you from going through the localiser (still wind)
Just a guess though, don't really know what I'm on about, not for operational use, caveat emptor and all that.
Its not a procedure turn by the way - a procedure turn is a way to reverse your course and hopefully come out on the reciprocal of the inbound track. The common one's are an 80/260 or a 45/180 with a one minute outbound leg. The immelmann is less common in IFR flying but you might get points for originality.
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From: London
I'm confused!
Hi
I have been having a look at the chart in the OP message, and following this thread. I am a bit confused, however, at the chart.
In the plan view, it suggests that BEA is close to the beginning of the runway, and that IBE is just beyond the runway.
However, in the profile view, it suggests that IBE is close to the beginning of the runway!
Confused!
I have been having a look at the chart in the OP message, and following this thread. I am a bit confused, however, at the chart.
In the plan view, it suggests that BEA is close to the beginning of the runway, and that IBE is just beyond the runway.
However, in the profile view, it suggests that IBE is close to the beginning of the runway!
Confused!
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From: On the Beach
tommoutrie:
Apples and oranges. The timing table is provided for the LLZ+DME procedureonly and only from the FAF inbound. Having said that, timing tables on DME-required IAPs are superfluous.
The chart posted by the OP is for CAT C and D. There is also a chart for CAT A and B with a narrower base leg. Finally, there is a DME ARC ILS chart, which makes use of the base leg procedures a bit ridiculous under most circumstances since DME is mandatory in any case. (three current charts follow):
At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less (plate only gives time and descent rate for up to 160) so a rate one will keep you from going through the localiser (still wind)
The chart posted by the OP is for CAT C and D. There is also a chart for CAT A and B with a narrower base leg. Finally, there is a DME ARC ILS chart, which makes use of the base leg procedures a bit ridiculous under most circumstances since DME is mandatory in any case. (three current charts follow):
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From: Blighty (Nth. Downs)
tommoutrie,
Quote:
“At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less...”
Must say your maths looks more impressive than the mental approximations I made in an earlier post, but the 194 kt (TAS) figure looked too low to me. So, as your conscientious co-pilot, I decided to do a gross-error check, looking at the first 180 degrees of the base turn.
I’ve made the following assumptions:
Still air;
Rate-one turn = 180 deg/min;
pi = 22/7 (although 3 would have been good enough for gross-error purposes);
r (radius of turn as drawn) = 2.1 nm (your figure, which is close to my earlier 1-in-60-rule approximation of 2nm);
Track miles for the 180-degree arc (semi-circumference) = pi * r
Therefore, as drawn, the first 180 degrees of the turn have a track distance of 22/7 * 2.1nm = 6.6 nm.
Note that this takes 1 minute at rate-one.
Track distance covered in 1 minute @ 194 nm/hr = 3.23 nm.
So the semi-circle of the 180-deg turn would be achieved in 3.2 nm, and that semi-circumference suggests a radius of turn of just over 1 nm. That’s almost exactly half the radius as drawn, so the aircraft would be way inside the drawn curve. Looks like a rate-half turn would be about right for that speed. (I refer you to my previous post.)
Ahem, SIR... Any chance you’ve used 2*pi*r as a formula for semi-circumference?
PS
Meant to point out earlier that rate-one is not achievable (“legally”) at 250 kt in civil ops, Pilots will recall that jet holding patterns are based on 25 deg bank or rate-one, whichever requires the lesser bank. (That means that if TAS is about 190 kt or more, rate-one is not achieved.) So if the pattern is based on 250 kt, it would probably assume 25 deg bank. Can you tell us what turn-rate that would be?
cruisege2,
It’s very simple. The plan (azimuth) view shows the ILS localiser (LLZ) “beam” emitted from an antenna array past the upwind (far end) of the runway. The vertical profile shows the separate glide-slope (GS) “beam” emitted from an antenna to the side of the runway, abeam the touchdown point.
Quote:
“At 250 it works out to be substantially more than a rate one turn so I doubt the plate was ever drawn to cope with aircraft that fly a base turn at 250. Its actually a rate one turn for an aircraft flying at 194 kts(ish). So my guess is that the procedure is probably drawn for aircraft flying the base turn at 185 or less...”
Must say your maths looks more impressive than the mental approximations I made in an earlier post, but the 194 kt (TAS) figure looked too low to me. So, as your conscientious co-pilot, I decided to do a gross-error check, looking at the first 180 degrees of the base turn.
I’ve made the following assumptions:
Still air;
Rate-one turn = 180 deg/min;
pi = 22/7 (although 3 would have been good enough for gross-error purposes);
r (radius of turn as drawn) = 2.1 nm (your figure, which is close to my earlier 1-in-60-rule approximation of 2nm);
Track miles for the 180-degree arc (semi-circumference) = pi * r
Therefore, as drawn, the first 180 degrees of the turn have a track distance of 22/7 * 2.1nm = 6.6 nm.
Note that this takes 1 minute at rate-one.
Track distance covered in 1 minute @ 194 nm/hr = 3.23 nm.
So the semi-circle of the 180-deg turn would be achieved in 3.2 nm, and that semi-circumference suggests a radius of turn of just over 1 nm. That’s almost exactly half the radius as drawn, so the aircraft would be way inside the drawn curve. Looks like a rate-half turn would be about right for that speed. (I refer you to my previous post.)
Ahem, SIR... Any chance you’ve used 2*pi*r as a formula for semi-circumference?
PS
Meant to point out earlier that rate-one is not achievable (“legally”) at 250 kt in civil ops, Pilots will recall that jet holding patterns are based on 25 deg bank or rate-one, whichever requires the lesser bank. (That means that if TAS is about 190 kt or more, rate-one is not achieved.) So if the pattern is based on 250 kt, it would probably assume 25 deg bank. Can you tell us what turn-rate that would be?
cruisege2,
It’s very simple. The plan (azimuth) view shows the ILS localiser (LLZ) “beam” emitted from an antenna array past the upwind (far end) of the runway. The vertical profile shows the separate glide-slope (GS) “beam” emitted from an antenna to the side of the runway, abeam the touchdown point.
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From: On the Beach
Since most pilots don't do algebra or trig in the terminal area a better idea might to slow a jet to 200 KIAS, or so, prior to the base leg turn point, and a prop jock to perhaps 140 KIAS, or so.
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From: london, UK
Hey I did put a caveat and I did point out that I'm totally clueless. And I'd got it a bit wrong. At 250 kts you'd need a bank angle of 34.5 to do a rate one turn. You would need a bank angle of 23.5 to do the base turn depicted on the chart. So I suppose you could fly it at 250 (I couldnt, if I'm not at 160 at about 10 miles I am screwed..) But that doesn't allow for rolling in or rolling out, you need a margin for wind, and that's actually using formula for a weight on a string rather than a plane so it doesn't allow for any slip or skid (yaw) and there are probably other inaccuracies too. One I can't quantify is that if you have 90 degrees of bank your radius of turn is 0 which is obviously rubbish and will have something of an effect at lower bank angles. I suspect the "spinning things round on a string" equation gets less and less accurate the steeper the bank angle.
Its interesting that 185 knots is exactly coincident with the max bank angle that my autopilot can command (27 degrees) and thats the bit of maths I had got wrong. I originally worked that out to 194 but I can't count. I had used 27 degrees as a max bank angle during the base turn. But I don't know if there's actually a max bank angle you can use - in JAA land they get a bit squiffy if you go outbound supersonic but americans have different rules.
the question about the localiser and the DME range - look at the difference in the ranges and you can see how far apart they are (0.2NM or maybe 1200 feet) so the drawing probably isn't awful. They are not usually exactly to scale though - look at the 3.8 distance compared to the 6.
for the OP - you're just trying to establish on the inbound track rather than making a pretty curve that intercepts the final approach track but if it helps, for this geometry, you could try
185 kts, 14 degrees
160 kts, 10 degrees
140 kts, 8 degrees
still wind, and see what happens. If it doesn't work, don't blame me
Its interesting that 185 knots is exactly coincident with the max bank angle that my autopilot can command (27 degrees) and thats the bit of maths I had got wrong. I originally worked that out to 194 but I can't count. I had used 27 degrees as a max bank angle during the base turn. But I don't know if there's actually a max bank angle you can use - in JAA land they get a bit squiffy if you go outbound supersonic but americans have different rules.
the question about the localiser and the DME range - look at the difference in the ranges and you can see how far apart they are (0.2NM or maybe 1200 feet) so the drawing probably isn't awful. They are not usually exactly to scale though - look at the 3.8 distance compared to the 6.
for the OP - you're just trying to establish on the inbound track rather than making a pretty curve that intercepts the final approach track but if it helps, for this geometry, you could try
185 kts, 14 degrees
160 kts, 10 degrees
140 kts, 8 degrees
still wind, and see what happens. If it doesn't work, don't blame me
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The design of the base turn template should include an allowance for an omnidirectional wind of about 52kts. This includes the most adverse effect of that wind on the aircraft during the turn.
The variables are:
TAS, wind speed, rate of turn (max 3deg/sec, can be less), wind effect on turn, fix tolerances, tracking tolerances. If the base turn is timed, then timing tolerances are also included.
It all adds up to a large area ....
The variables are:
TAS, wind speed, rate of turn (max 3deg/sec, can be less), wind effect on turn, fix tolerances, tracking tolerances. If the base turn is timed, then timing tolerances are also included.
It all adds up to a large area ....
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From: london, UK
I remember finding a reference to 100kmh somewhere when I was in a hotel room and reading about procedure design so that sounds about right. The dodgy channel was broken, the other crew member was ill, there was nothing to do, I didnt meant to read it, it just happened.
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From: London
Chris wrote: It’s very simple. The plan (azimuth) view shows the ILS localiser (LLZ) “beam” emitted from an antenna array past the upwind (far end) of the runway. The vertical profile shows the separate glide-slope (GS) “beam” emitted from an antenna to the side of the runway, abeam the touchdown point.
Thank you Chris, that explains a lot, but it does raise one further question. Which 'beacon' is the one that feeds the DME figures? With the two beacons potentially being a couple of miles apart, I am guessing that the pilot needs to know where exactly the 10 DME refers to!
Thank you Chris, that explains a lot, but it does raise one further question. Which 'beacon' is the one that feeds the DME figures? With the two beacons potentially being a couple of miles apart, I am guessing that the pilot needs to know where exactly the 10 DME refers to!
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From: Blighty (Nth. Downs)
Bank and g
Quote from tommoutrie:
"...that's actually using formula for a weight on a string rather than a plane so it doesn't allow for any slip or skid (yaw) and there are probably other inaccuracies too. One I can't quantify is that if you have 90 degrees of bank your radius of turn is 0 which is obviously rubbish and will have something of an effect at lower bank angles. I suspect the "spinning things round on a string" equation gets less and less accurate the steeper the bank angle."
No, it remains good. Forgive me for drifting off-topic, but I think tommoutrie's dilemma needs to be put to rest. To maintain level flight (or a steady climb or descent) and achieve a balanced turn (no slip or skid), acceleration ("g") in the normal axis simply has to be increased from the straight-and-level figure of 1.0 to whatever is appropriate for the bank angle.
As he/she knows, the formula is
normal g = 1/cos(bank angle)
Here are some samples of bank angle versus g:
0 deg = 1.0
15 deg = 1.035
30 deg = 1.155
45 deg = 1.414
60 deg = 2.0
66.5 deg = 2.508
75 deg = 3.864
80 deg = 5.759
83 deg = 8.206
85 deg = 11.47
87 deg = 19.11
88 deg = 28.65
89 deg = 57.30
89.5 deg = 114.6
90 deg = infinity
At flying school, we've all done lovely, balanced, steep turns with 60 deg bank, pulling 2g and maintaining height. If you can pull enough g, you can maintain level flight (or a steady climb or descent) in a balanced turn at a given bank angle. But if your aerobatic aeroplane is limited to +6g, it will not be able to sustain a balanced turn at more than 80 deg bank without falling at an increasing rate. And a BALANCED turn with 90 deg bank is impossible.
"...that's actually using formula for a weight on a string rather than a plane so it doesn't allow for any slip or skid (yaw) and there are probably other inaccuracies too. One I can't quantify is that if you have 90 degrees of bank your radius of turn is 0 which is obviously rubbish and will have something of an effect at lower bank angles. I suspect the "spinning things round on a string" equation gets less and less accurate the steeper the bank angle."
No, it remains good. Forgive me for drifting off-topic, but I think tommoutrie's dilemma needs to be put to rest. To maintain level flight (or a steady climb or descent) and achieve a balanced turn (no slip or skid), acceleration ("g") in the normal axis simply has to be increased from the straight-and-level figure of 1.0 to whatever is appropriate for the bank angle.
As he/she knows, the formula is
normal g = 1/cos(bank angle)
Here are some samples of bank angle versus g:
0 deg = 1.0
15 deg = 1.035
30 deg = 1.155
45 deg = 1.414
60 deg = 2.0
66.5 deg = 2.508
75 deg = 3.864
80 deg = 5.759
83 deg = 8.206
85 deg = 11.47
87 deg = 19.11
88 deg = 28.65
89 deg = 57.30
89.5 deg = 114.6
90 deg = infinity
At flying school, we've all done lovely, balanced, steep turns with 60 deg bank, pulling 2g and maintaining height. If you can pull enough g, you can maintain level flight (or a steady climb or descent) in a balanced turn at a given bank angle. But if your aerobatic aeroplane is limited to +6g, it will not be able to sustain a balanced turn at more than 80 deg bank without falling at an increasing rate. And a BALANCED turn with 90 deg bank is impossible.
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From: On the Beach
Mr. Good Cat:
It makes sense only to those who are actually trained and actually fly aircraft under instrument flight rules.
The ident of the DME referred to is under the stated distances I.e. 10.2 with IBE written underneath clearly shows which DME the point is referenced to, if that makes sense?
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From: Blighty (Nth. Downs)
Question fom cruiseqe2:
"Which 'beacon' is the one that feeds the DME figures? With the two beacons potentially being a couple of miles apart, I am guessing that the pilot needs to know where exactly the 10 DME refers to!"
The short answer, of course, is neither! DME ground "reply" transmissions are on a higher UHF frequency than the ILS GS, and the ILS LLZ is on VHF. (Note that the flight crew, if selecting the ILS manually on their radio management panel, have only to dial up the LLZ frequency - 108.7 in this case - to tune all three elements.)
But it is clear from the way the final-approach procedure is drawn that this ILS-DME reads zero, effectively, at the touchdown point. Therefore the ILS-DME receiver-transmitter is probably very close to the GS transmitter, if not on the same spot. The EAG training chart (link provided by the original poster) has more detail than the Jeppesens, and the clue seems to be on the profile, which shows a "D" and "IBE" above the touchdown point.
aterpster and others may think I'm being pedantic to labour an obvious point, but it's not always this simple. In the USA, many ILS-DMEs are sited at the LLZ aerial, and read the appropriate DME distance in n.m. at the touchdown point (e.g., 2.0). In the past, I've flown at airfields where the two ILSs on opposite runways used one ILS-DME receiver-transmitter in the middle of the airfield, which biassed its transmissions to read zero at both thresholds. Then there was another airfield, EGKK, with a similar setup except that the DME was not equidistant from the two thresholds. So the bias had to be altered when ATC changed runways. That sometimes caused confusion during the changeover, particuarly when it was being used for departure navigation (SIDs), but I think they later rectified that anomaly.
"Which 'beacon' is the one that feeds the DME figures? With the two beacons potentially being a couple of miles apart, I am guessing that the pilot needs to know where exactly the 10 DME refers to!"
The short answer, of course, is neither! DME ground "reply" transmissions are on a higher UHF frequency than the ILS GS, and the ILS LLZ is on VHF. (Note that the flight crew, if selecting the ILS manually on their radio management panel, have only to dial up the LLZ frequency - 108.7 in this case - to tune all three elements.)
But it is clear from the way the final-approach procedure is drawn that this ILS-DME reads zero, effectively, at the touchdown point. Therefore the ILS-DME receiver-transmitter is probably very close to the GS transmitter, if not on the same spot. The EAG training chart (link provided by the original poster) has more detail than the Jeppesens, and the clue seems to be on the profile, which shows a "D" and "IBE" above the touchdown point.
aterpster and others may think I'm being pedantic to labour an obvious point, but it's not always this simple. In the USA, many ILS-DMEs are sited at the LLZ aerial, and read the appropriate DME distance in n.m. at the touchdown point (e.g., 2.0). In the past, I've flown at airfields where the two ILSs on opposite runways used one ILS-DME receiver-transmitter in the middle of the airfield, which biassed its transmissions to read zero at both thresholds. Then there was another airfield, EGKK, with a similar setup except that the DME was not equidistant from the two thresholds. So the bias had to be altered when ATC changed runways. That sometimes caused confusion during the changeover, particuarly when it was being used for departure navigation (SIDs), but I think they later rectified that anomaly.
Last edited by Chris Scott; 22nd February 2013 at 20:04.
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From: On the Beach
Chris Scott:
Your statement in Post 35:
You may or may not have been implying that the Jepp charts were lacking. Thus my comment/point.
Your statement in Post 35:
The EAG training chart (link provided by the original poster) has more detail than the Jeppesens
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From: Blighty (Nth. Downs)
Hi aterpster,
I see what you mean. All charts have to be a compromise between need-to-know and nice-to-know, while avoiding clutter, and Jeppesen have got it about right from a pilot's viewpoint. I'm more familiar with what used to be called Aerad, but we always used Jeppesen when in the US. Never seen EAG before.
It happens that, on this occasion, the EAG chart illustrates the point I was making to cruiseqe2 about the siting of the DME. For practical piloting purposes, the Jeppesen charts have everything you need. On the KLAX ILS-DME charts, for example, there's a note at the top giving the DME readings at the thresholds.
BTW, thanks for posting those three.
I see what you mean. All charts have to be a compromise between need-to-know and nice-to-know, while avoiding clutter, and Jeppesen have got it about right from a pilot's viewpoint. I'm more familiar with what used to be called Aerad, but we always used Jeppesen when in the US. Never seen EAG before.
It happens that, on this occasion, the EAG chart illustrates the point I was making to cruiseqe2 about the siting of the DME. For practical piloting purposes, the Jeppesen charts have everything you need. On the KLAX ILS-DME charts, for example, there's a note at the top giving the DME readings at the thresholds.
BTW, thanks for posting those three.
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From: On the Beach
Chris Scott:
Where on the chart is that? The only DME reading for the threshold that I see is in the profile view; for example 24R:
D2.0
IOSS
In any case once I pass the P-FAF (JETSA) I am not concerned about DME readings with a full ILS, including that threshold DME reading. That is for the GS-out fellow. My missed approach point is predicated on DA. The next DME fix I might be concerned about after DA is:
RAFFS
D15.1 LAX
On the KLAX ILS-DME charts, for example, there's a note at the top giving the DME readings at the thresholds.
D2.0
IOSS
In any case once I pass the P-FAF (JETSA) I am not concerned about DME readings with a full ILS, including that threshold DME reading. That is for the GS-out fellow. My missed approach point is predicated on DA. The next DME fix I might be concerned about after DA is:
RAFFS
D15.1 LAX