Flying Safety: How to hold without losing your grip - airplane piloting

If you've looked at AFMAN 11-217, Instrument Flight Procedures, lately, did you notice anything interesting? Chapter 10, paragraph 10.3.5.1, says the maximum holding speed at and below 6000 ft is 200 knots and "Do not exceed the maximum holding speed listed..." Does that really apply to everyone? How about aircraft like the T-38 with a tech order holding speed of 250-265 knots? Does having Cat E minimums on the plate have any effect on those holding speeds? Well, let's see if we can put our arms around these and figure out how we can avoid a controlled flight into terrain (CFIT) in a holding pattern. We'll break this down into two parts: (1) How to apply the airspeed rules, and( 2) How much airspace you are dealing with in a holding pattern.

Part I--Just what do I do with all this airspeed guidance?

Holding is a hot topic these days. The Advanced Instrument School (AIS) has received numerous questions since the release of the new AFMAN 11-217 (dated 29 Dec 2000) regarding para 10.3.5. This paragraph has an eye-opening list of maximum holding airspeeds that have caught some pilots by surprise. Those speeds are very real. Knowing how and when they apply is the key to operating safely. Let's start with a little history lesson.

From 1961 to 1989, the maximum holding speeds for civil turbojet aircraft engaged in level or descending IFR flight operations (from Air Line Pilot, Feb 1994) were as follows:

* 200 KIAS from the minimum holding altitude through 6000 ft MSL

* 210 above 6000 MSL through 14,000 MSL

* 230 above 14,000 MSL

Climbs in holding were authorized 310 KIAS (250 below 10,000 MSL, where applicable).

230 KIAS at higher altitudes was just too slow for a clean, heavy aircraft like those typically used in transport. So in 1989 the FAA increased the airspeeds to 230 KIAS at and below 14,000 and 265 KIAS above 14,000. Unfortunately, they didn't change the size of the holding patterns to accommodate those new airspeeds. Those patterns previously designed for 200 KIAS were now being flown at 230 KIAS. Pilots were playing Russian Roulette in those patterns. The Air Line Pilots Association (ALPA) caught onto this problem and issued Safety Alert Bulletin No. 93-6 "Maximum Authorized Holding Speeds for Turbojet Aircraft." It stressed that it may not be safe to hold at 230 KIAS at 14,000 MSL and below.

That problem has been rectified and the current FAA Order 7130.3A, Holding Pattern Criteria, now specifies holding patterns based on the airspeeds listed in the table in AFMAN 11-217. In addition, the FAA order contains a table listing recommended holding speeds for various military aircraft, should the designer be interested in designing the holding pattern to accommodate those aircraft. AFI 11-230 (the supplement to the TERPs manual, AFMAN 11-226) stipulates that all AF-designed holding patterns will be designed for a maximum holding speed of 310 knots at all altitudes. As with anything, there are exceptions, and those will be noted in the procedure.

So, where does all that put us today? As with anything... it depends. It is sometimes difficult to discern just exactly what standards were applied when the holding pattern was designed. If the holding pattern was designed by the Air Force, the holding airspeed can be considered to be 310 KIAS maximum, unless indicated otherwise in the procedure. If the FAA designed the pattern, it would be wise to apply those airspeeds now listed in AFMAN 11-217 paragraph 10.3.5.1 and AIM Table 5-3-1, in order to be safe. The Navy designs all holding patterns for 230 knots at all altitudes, unless noted otherwise. The Army contracts the FAA to do their approaches, so civil speeds apply at Army fields. Holding patterns designed to maximum holding speeds other than standard (including those at USAF airfields not built for 310 KIAS) will be annotated with an icon on the procedure stating the maximum holding airspeed.

Pay particular attention to the wording in AIM 5-3-7 j.2(b)(3): "Holding patterns at USAF airfields only--310 KIAS maximum, unless otherwise depicted." Notice that it says USAF airfields. The reason is that if you are flying an approach at a civilian airfield and happen to notice that the approach has "(USAF)" at the top of the plate, there is no guarantee the USAF actually designed that approach. Take a look at the HI-ILS RWY 3 at San Angelo Regional in the High SW approach book. It says "JAL-376.01 (USAF)" at the top of the plate, so we might assume the holding pattern depicted at the JAF, RANGE, has a maximum holding speed of 310 knots since the plate says "(USAF)." This is a bad assumption. An FAA designer may have produced the procedure on behalf of the USAF (we are told that is actually the case at SJT). In that case, FAA civil holding airspeeds may have been applied; you have no way of knowing simply by looking at the plate.

Remember, AIM says USAF airfields. Sometimes this can be confusing as well. Take Scott or Sheppard AFBs as examples. In both of these cases, you have both FAA and USAF TERPs designers building approaches to the same field. According to AFFSA, the FAA is now designing all of the procedures at Scott AFB, so civil rules may apply. Even at those fields, seeing "(USAF)" at the top of the plate doesn't guarantee a USAF designer built the approach (although that was probably the case). The lines get blurred. Fortunately Sheppard and Scott are very rare scenarios. At both of those fields, it might be wise to take the conservative stance if you are in doubt.

OK, so we know what the AIM, FAA Order 7130.3A and AFI 11-230 all have to say about maximum holding airspeeds. Just how does Joe Pilot apply all this newfound information? First, start by applying the guidance in AFMAN 11-217 and comply with paragraph 10.3.5. If you are holding at anything other than a USAF airfield, the safest thing to do is to apply the airspeeds listed in the table, unless some other airspeed is noted on the procedure or you have specific guidance to do otherwise. A good example of this guidance is FLIP GP Chapter 5. It tells us that Navy holding patterns are 230 knots. If you are at an Air Force base (not a joint AF/civil field), it is safe to assume the max holding speed is 310 KIAS unless posted otherwise. If it is a joint use AF/Civil field, it would be wise to play it safe and fly civil holding speeds unless the procedure is annotated with higher airspeeds, regardless of whether it says "(FAA)" or "(USAF)" at the top of the plate. If the standard or posted holding speed is too slow fo r your aircraft, simply ask for a faster holding speed from ATC. In almost all cases, it will be granted unless there are legitimate airspace or obstacle concerns. If you find yourself arriving at a holding pattern while NORDO, IMC and unable to coordinate for faster holding speeds, you need to figure out some way to apply the standard holding speeds while in the pattern. That may mean slowing and lowering flaps, or something similar.

By the way, it should be apparent now that seeing category E minimums on the bottom of the plate has nothing to do with the holding airspeeds designed into the procedure.

Part II--How much airspace are we talking about?

AFMAN 11-217 paragraph 10.4.1 says this about entering the holding pattern: "The aircraft must cross the holding fix, turn outbound and remain within the holding airspace." This begs the question, "Just how do I tell if I remain in holding airspace?"

Let's look at Figure 1. This is a depiction of one of the templates used by an approach designer to draw a holding pattern (numbers from FAA Order 7130.3A). This template is used for a holding pattern at 8000 feet MSL, 230 knots and a holding fix from between 15 DME and 29.9 DME from the NAVAID, a fairly typical holding pattern.

The outline defines the primary obstacle clearance area. There is the standard 1000 feet of obstacle clearance (2000 feet in mountainous areas) inside the out-lined area. In addition, outside the primary there is a secondary area that is the same shape but 2 NM larger all the way around. The obstacle clearance in this area would begin at 500 feet and taper off to zero feet at the outer edge. The distances shown on the figure (from Table 3 of 7130.3A) are there to give you an idea of the exact size of this particular holding area.

As you can see, the overall area is quite large, and the area on the maneuvering side is larger than on the non-maneuvering side. The maximum DME leg length allowed in this particular pattern is 8 NM. The length of the pattern on the holding side of the fix is 16.7 NM. So there is obviously some slop built in there somewhere. Why so much extra space?

Well, some assumptions are taken when designing the size of the holding airspace. First, there is system error; [+ or -] 5 degrees is allowed for the ground station error, airborne equipment error (VOR/TACAN receiver) and pilot error. At 15 DME, that equates to approximately 1.3 NM of displacement at the fix. Second, there is an allowance to [+ or -] 10 degrees for full scale CDI deflection; that's another 2.65 NM at 15 DME. Third, there is six seconds of reaction time added for the pilot to recognize fix passage. Lastly, there is a wind allowance of 50 knots starting at 4000 MSL and increasing by three knots every 2000 feet; that's 56 knots of wind at 8000 MSL. This wind is applied in the most detrimental direction at all points in the pattern. There is an allowance for the "cone of confusion" if the fix is overhead a station, but it doesn't apply in this example. If we were to discuss a holding fix that is directly over a VOR, the numbers would still come out very close to the ones I'm using.

Let's take a look at the holding pattern, apply the assumptions and see how an aircraft flying at 230 KIAS would do in this pattern. At 230 KIAS, 8000 MSL the TAS is approximately 260 knots on a standard day. That gives a turn radius of approximately 1.7 NM. If the aircraft hits the holding fix tracking directly down the radial inbound and turns using 30 degrees of bank in the direction of holding, its turn diameter will be 3.4 NM. In addition, the aircraft might be off by 1.3 NM (system error) at the start of the turn and that 56 knot wind will blow it another 1.5 NM during the turn. That totals up to 6.2 NM of displacement from the holding fix when the aircraft rolls wings-level outbound (see Figure 2, track A).

Notice from Figure 1 that the primary area is approximately 7.8 NM wide abeam the fix; the aircraft is still inside the template. What about the [+ or -] 10 degrees allowed for full-scale CDI deflection? Well, it should be obvious that hitting the fix dead-on is the way to go. However, if you happen to be offset to the maneuvering side of the pattern and subsequently also turn into the direction of holding, you are going to find yourself displaced more than 6.2 NM when you roll wings level (Figure 2, track B). Exactly how much will depend on how far off course you were at the turn. If you were displaced a full 10 degrees, that would equal approximately 2.6 NM of displacement at 15 DME. Add that 2.6 NM to the original 6.2 NM and you are now 8.8 NM displaced from the fix. Keep in mind that the primary holding area only went out to approximately 7.8 NM at this point in the pattern. You are a mile into the secondary obstacle clearance area of the holding pattern...still safe, but your margin of error is shrinking fast! If you apply appropriate wind-drift corrections for the remainder of the pattern, you will remain inside of the secondary protected airspace. If you let the wind continue to blow you off course, you may be outside of the secondary area when you begin the turn inbound.

If you are displaced to the non-maneuvering side of the pattern (Figure 2, Point C), you had better think twice before turning left; you'll fly outside protected airspace if all the negative factors are working against you. Furthermore, AFMAN 11-217 paragraph 10.4.1 doesn't require you to apply the time-tested holding entry rules we all grew up with: "within 70 degrees, turn in the direction of holding." You could legally hit the fix and turn any direction you want, but is that wise? If you hit the fix as in the first example and turn left instead of right, you will go .9 NM outside of the primary holding airspace if all the negative factors are working against you. Is a left turn in that case ensuring you remain within holding airspace? No.

You can swing those turn arcs around to simulate entering the pattern from various different angles over the fix, but all of them will fail inside the paths in Figure 2 by some degree.

We could continue along these same lines and analyze the other end of the pattern. The short of it is this: With all the negative assumptions at play, if you are flying a DME holding pattern and turn inbound at the correct DME (in the above examples that would be 23 DME), you will swing out to just over 26 DME (turn radius, winds and a late turn due to standard 3% DME error) before your turn starts bringing you inbound. The farthest point in our example pattern is out to 31.7 DME; plenty of room. If you do a timed pattern in this example, you would have even more room because a one-minute pattern would equate to less than an 8 DME holding pattern by over two miles.

Wrap it Up

I hope all this techno-babble puts the new guidance in AFMAN 11-217 regarding holding airspeeds into focus. In the above exercise, if you entered that very same pattern at 265 knots instead of 230, you could easily find yourself outside of protected airspace if all the factors came into play at once. It's critical that you adhere to the appropriate airspeeds.

Additionally, you'll notice that AFMAN 11-217 paragraph 10.4.1 says, "The aircraft must cross the holding fix, turn outbound and remain within the holding airspace." That is all it has to say with regard to what is procedure. Para. 10.4.4 talks about the standard entry "techniques." If you choose not to use those techniques, you had better have full and complete situational awareness of where you are in space and where your turn will take you. A wrong turn could spell disaster. Hopefully, the discussion above gives you an example of just how big that "holding airspace" really is and what you need to do to ensure you remain within it.

My recommendations:

1. Do a good fix-to-fix, and nail the holding fix.

2. Apply known wind corrections, and be conservative.

3. Do not fly faster than the pattern is designed for, unless you have ATC monitoring and permission to do so.

4. Don't freelance the entry. Know where you are when you enter, and enter in a calculated manner (the techniques in AFMAN 11-217 work well, as do the holding entry diagrams on the IAP). If you're flying ICAO, apply the ICAO entry procedures (para. 23.5.4).

5. Apply the holding speeds listed in AFMAN 11-217, if you aren't sure what speeds apply, regardless of what your T.O. says. Exceptions are USAF airfields (310 knots) and Navy (230 knots unless posted otherwise).

Fly safe!