What is the obstacle clearance while holding?

[italia458]

Title pretty much says it all. If someone could give me a Canadian answer that'd be great but any ICAO answer would probably be pretty close to Canada.

The procedure turn has well defined obstacle clearance distances and there is obviously either a Minimum Holding Altitude or min IFR altitude at which those dimensions will be applicable. I can't find anything like that for holds though.

[aterpster]

Canada uses U.S. TERPS. There are approximately 30 different size pattern templates that are used for approximately 120 combinations of altitude and speed. If you follow the holding procedures you will have not less than 1,000 feet of vertical obstacle clearance throughout the holding pattern.

The exception is a climb in hold that is close to the airport such as the KGCN ILS missed approach.

[JAR]

A link- may be out of date - page I-6-2-1 and I 6-2-2

http://dcaa.slv.dk:8000/icaodocs/Doc%208168%20-%20Aircraft%20Operations/Volume%201%20Flight%20Procedures,%205th%20ed..pdf

[italia458]

JAR... thanks for that doc! I didn't find my answer in it but it led me to the Volume 2 of ICAO 8168 which goes into detail on the constructing of flight procedures. It basically goes over formulas for calculating the primary area. And based on those formulas it could come up with an infinite number of holding area dimensions. I'm sure they've lowered that number to a more useable one though! I think for the practical pilot it would be good enough to say that if he follows the holding procedures (timing, distance, speed and bank angle) he should be just fine!

Here it is: http://dcaa.slv.dk:8000/icaodocs/Doc%208168%20-%20Aircraft%20Operations/Volume%202%20-%20Construction%20of%20Visual%20and%20Instrument%20Flight%20 Procedures.pdf

[aterpster]

Canada uses TERPS!
:)

PANS-OPS is not applicable.

[italia458]

ater... do you have a reference for that? I've heard from other ppl that Canada uses TERPS but don't have a reference.

[reynoldsno1]

based on those formulas it could come up with an infinite number of holding area dimensions

The holding area dimensions are not infinite, but will vary according to speed, altitude, temperature and time (or distance). Angle of bank is fixed. Designers usually fix the temperature at ISA + an appropriate amount (+15 in temperate climates). There are computer programs that will draw the holding templates for you.

[FlightPathOBN]

No need for the math model...

Canada uses TERPS, hold patterns are a pre-defined racetrack...

FAA Order 7130.3A, “Holding Pattern Criteria,” contains the containment criteria for all FAA holding patterns. The criteria assumptions contained in this order are predicated on a March 31, 1964 order, FAA Handbook AT P 7130.8, “Development of Holding Pattern Criteria and Procedures.” 31 holding pattern templates were developed to fit over 100 different combinations of indicated airspeed (IAS), altitude, and distance from facility in the case of ground-based navaids. Averaged seasonal winds aloft were part of this extensive 1964 evaluation.

For RNP procedures, the templates have been reduced to only 5 choices.

[aterpster]

italia458:

ater... do you have a reference for that? I've heard from other ppl that Canada uses TERPS but don't have a reference.

Yes, I do. Peruse this Transport Canada link:

Advisory Circular (AC) No. 803-001 - Transport Canada (http://www.tc.gc.ca/eng/civilaviation/opssvs/managementservices-referencecentre-acs-800-803-001-133.htm)


Also, the circle to land speeds on Canadian IAPs are consistent with TERPs, not PANS-OPS.

[aterpster]

FltPathOBN:

For RNP procedures, the templates have been reduced to only 5 choices.

Where is that set forth?

Certainly not in FAA Order 8260.52.

Course reversal holding is not authorized under that order for RNP AR IAPs.

Missed approach holding can be used where RNP missed approach criteria are terminated or non-RNP missed approach criteria are used. The missed approach holding pattern criteria selection is standard TERPs from Order 7130.3A.

RNP holding has yet to be formulated.

[italia458]

No need for the math model...

Canada uses TERPS, hold patterns are a pre-defined racetrack...

Yes, holds are a pre-defined racetrack, however, the obstacle clearance is a mathematical model.

reynoldsno1... The mathematical formulas has a "potential" for an infinite number of obstacle clearance dimensions.

However, based on the mathematical formulas, they have narrowed it down to a number of possible obstacle clearance models. The formulas are based on speed, temp, etc. and so the obstacle clearance models are also based on that.

ater... thanks for the reference! It seems that everyone has their own set of rules. Canada being based off of TERPS and, if I'm not mistaken, TERPS is based off of PANS-OPS. In any case, they're all pretty similar.

[FlightPathOBN]

Terpster,

They are not new ones, but limited use of existing, with altitude and IAS because only distance is important as it is not timed reliant, FAAO 7130.3A.

[aterpster]

FlightPathOPN:
They are not new ones, but limited use of existing, with altitude and IAS because only distance is important as it is not timed reliant, FAAO 7130.3A.

I can only speak for the application of FAAO 7130.3A in airspace under FAA jurisdiction:

1. All RNAV course reversal and missed approach holding patterns use legs predicated on distance rather than time.

2. Pattern selection is made based on Table 2 (Holding Pattern Selection Chart) maximum holding altitude and speed from the 15-29.9 fix-to nav aid distance column based on AFS-420 memo for RNAV holding.

3. The speed selection for jet aircraft is 200 KIAS through 6,000, 230 KIAS through 14,000, and 265 KIAS above 14,000. 310 KIAS patterns are used for climb-in-hold.

4.Construction is in accordance with Figure 10 on Page 2-15 and Table 3 (Page 2-16) with a 2 n.m. secondary added for TERPs. (This construction can be done manually for those without the automation tools.)

5. End area reductions and on-entry reductions of the Figure 10 construction, which are permitted for qualified ATC holds, are not permitted for IAP holds.

6. RNAV leg length to be charted is selected from Table 8 on Page 6-3.

This is the method for all RNAV including RNP AR, except (as I stated previously) course reversal holding patterns are not used in RNP AR construction but often used in other RNAV IAPs. Other than this limitation on course-reveral holding patterns in RNP AR all other holding patterns are identical for RNP AR or any other RNAV IAP.

All FAA holding patterns are documented on FAA TERPs Form 8260-2.