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Q & A

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Over the years I've probably got several thousands of questions on the web and, I am afraid to say, I hardly ever make a record of them. I know this because sometimes when I am researching an answer, I realize that I once answered the question before. If only I had captured it the first time! Well let's see if we can fix that.


Approach Categories?

Is your approach category based on your actual or your maximum certificated landing weight. To me the answer was always obvious but there are many who read 14 CFR 97.3 a different way, all based on a single comma. I think we have more than a few pilots out there flying the wrong approach category. They will tell you that I don't know what I am talking about. In 2013 the FAA settled the matter but haven't changed the regulation to remove the confusion. Don't be confused, read on.

More about this: Approach Categories.

Dear Eddie,

I read that you claim my approach category is based on my maximum landing weight but that isn't what they taught me at Brand X Simulator company, where all the instructors are experts. They tell me that if we did that in our Challenger, we wouldn't be able to fly into Aspen and nobody believes that. Besides, isn't what we are worried about the actual maneuverability of the aircraft? So if I am 10,000 pounds below maximum landing weight, shouldn't I be allowed to fly the approach category that fits that speed? I've read Part 97.3 several times and I think the maximum landing weight only applies to aircraft that do not have a VREF, which ain't me.

Signed, R. Fader
Fort Lee, New Jersey

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Photo: Circling at Hilo, Hawaii

Click photo for a larger image

Mister Fader,

I have been wrestling with this issue for many years, but in 2013 the FAA finally cleared it all up. The bottom line is this: you must use the maximum certificated landing weight, even if you have a VREF.

Eddie

[14 CFR 97.3] Aircraft approach category means a grouping of aircraft based on a speed of VREF, if specified, or if VREF is not specified, 1.3VSO at the maximum certificated weight. VSO, and the maximum certificated landing weight are those values as established for the aircraft by the certification authority of the country of registry.

These categories are as follows:

  • Category A: Speed less than 91 knots
  • Category B: Speed 91 knots or more but less than 121 knots
  • Category C: Speed 121 knots or more but less than 141 knots
  • Category D: Speed 141 knots or more but less than 166 knots
  • Category E: Speed 166 knots or more

There are some who would argue that maximum certificated weight only applies to 1.3VSO based on the placement of a comma in the regulation. The debate raged on for decades but the FAA finally provided some clarity in 2013:

[14 CFR 97.3 Interpretation]

  • This memorandum is in response to your request for legal interpretation on the meaning of "aircraft approach category" as defined 14 C.F.R. § 97.3 dated September 24, 2012. Specifically you ask if the phrase "maximum certificated landing weight" as used in § 97.3 applies to aircraft grouped by speed of VREF. The answer to your question is "yes" the phrase "maximum certificated landing weight" applies to both aircraft grouped by speed of VREF as well as aircraft grouped by 1.3 VSO.
  • In 1972 the FAA implemented the U.S. Standard for Terminal Instrument Procedures (TERPS). The TERPS rule changed the way the FAA defined aircraft approach categories from one based on the number of engines to new criteria based on stall speed in landing configuration or aircraft weight. Specifically "aircraft approach category" was defined as a "grouping of aircraft based on a speed of 1.3 VSO (at maximum certificated landing weight) or on maximum certificated landing weight." See 32 Fed. Reg. 13909,13911-12 (Oct 6, 1967); 32 Fed. Reg. 6938, 6939 (May 5, 1967). Section 97.3 was amended later to remove the option for basing aircraft approach categories strictly on maximum certificated landing weight. See 44 Fed. Reg. 15659 (Mar. 15, 1979). The only remaining way to make this determination was "1.3 VSO (at maximum certificated landing weight)." Id.
  • In 1996 the FAA proposed replacing "1.3 VSO" with "VREF" in the definition of "aircraft approach category" in § 97.3. See 61 Fed. Reg. 1260, 1263 (Jan. 18, 1996). The proposed definition specified that aircraft would be grouped "based on a speed of VREF at the maximum certificated landing weight." Id. at 1268. After additional review, the FAA determined that application of the VREF standard "to aircraft certificated using VS could cause confusion for users of the airspace system and that some airplane flight manuals would not be consistent with the new VREF terminology. See 67 Fed. Reg. 70812, 70822 (Nov. 26, 2002). Therefore, the FAA revised § 97.3 in the final rule to "continue to reference 1.3 VSO for use in those cases where VREF is not specified." Id.
  • The regulatory history demonstrates that the FAA intended the "maximum certificated landing weight" qualifier to apply to aircraft for which either VREF or 1.3 VSO are used to determine approach category. The new VREF standard as proposed in 1996 required "maximum certificated landing weight" to be part of the determination. The FAA revised the final rule so that aircraft approach categories could still be determined using the existing "1.3 VSO at maximum certificated landing weight" standard in addition to the VREF standard proposed in the NPRM. The preamble to the final rule contained no discussion of removing the reference to maximum certificated landing weight for the VREF standard proposed in the NPRM. We therefore conclude that for aircraft grouped by speed of VREF aircraft approach category must be determined using speed of VREF at the maximum certificated landing weight.

On Course or Established?

Dear Eddie,

When can I consider myself “on course” or “established” for an approach? Everyone says just wait until the CDI is “off the wall” and you will be okay. I want to descend as soon as possible but how can I be sure I have obstacle clearance?

Signed, R. Fader
Fort Lee, New Jersey

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Photo: Proceeding Direct, from AFM 51-37.

Click photo for a larger image

Mister Fader

I flew my first ILS looking at a course indicator and was told the same thing: I could consider myself on course when the CDI came "off the wall."

On a procedure turn, for example, it was okay to descend to the inbound altitude once the CDI was no longer fully deflected.

Years later I adopted a "centered or nothing" attitude, thinking I was better than a nearly fully deflected needle.

But it begs the question, do we have the required obstacle clearance when the needle just comes off the wall. If not, what about one dot?

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Photo: Localizer final trapezoid, from Eddie's notes.

Click photo for a larger image

FAA Handbook 8083-15B, Instrument Flying Handbook, says one-quarter scale deflection means the airplane is aligned with the runway and full-scale deflection shows when the aircraft is 2.5° either side of centerline.

You cannot come up with a one size fits all rule about what full scale CDI deflection means. But doing the math, there are times when the needle comes off the wall a little early. I show that math on this website page: http://code7700.com/ils.htm#oncourse

So full scale is too much, waiting until the needles are centered can leave you too high for the procedure. But the FAA guidance is ambiguous. I think you should look at the ICAO Regs on this, ICAO Doc 8168, Procedures for Air Navigation Services, or PANSOPS, to be specific.

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Photo: ICAO "On Course," from ICAO Doc 8168.

Click photo for a larger image

That regulation says the tracking tolerance of the localizer/azimuth is much more narrow than for non-precision approaches and gives us the worst case scenario. In that scenario, “half scale deflection” keeps you in the protection area.

So in my opinion, that’s a good time to consider yourself on course or established: half scale deflection.

Eddie

Half of What Wind and All of What Gust?

More about this: Landing.

Eddie,

We all know we have to add half the wind and the full gust increment to our approach speeds. But do you add half the wind, or half the headwind?

Signed, R. Fader
Fort Lee, New Jersey

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Photo: Crosswinds, MROC, 21 Feb 2012, Bernal Saborio

Click photo for a larger image

Mister Fader,

This has vexed me for a long time, but there is a more important question. But first, to answer your question. It depends on your manufacturer. Most simply state the wind itself, they don't want you doing the headwind component. Gulfstream, for example:

[G450 Airplane Flight Manual §5.11] If gusty wind conditions are present, add ½ of the steady state wind plus the full gust value to a maximum additive of 20 knots (VREF + 20). VREF will still be the target speed at the threshold.

Bombardier aircraft have a similar statement.

The other method is used by Boeing, in the 737NG, for example:

[Boeing 737 GN FCTM, p. 1.11] If the autothrottle is disconnected, or is planned to be disconnected prior to landing, the recommended method for approach speed correction is to add one half of the reported steady headwind component plus the full gust increment above the steady wind to the reference speed. The minimum command speed setting is VREF + 5 knots.

Dassault has a similar method and they have an even better explanation:

[F900EX CODDE2, ] Approach speed (VAPP) is the result of: VREF + wind correction. For wind correction (maximum 20 kt): apply half headwind + full gust increment. COMMENTS: The gust value should be taken into account whatever the wind direction is. For example for RWY 18, wind 120/20G30 given by the ATC: the steady state headwind component is 10 kt (crosswind component is 17 kt) and the full gust is 10 kt so the wind correction should be 15 kt (which is less than 20 kt).

So the technical answer depends on your aircraft manuals, but I think the right answer, the one that takes physics into consideration, has more to do with my bigger concern: stall speeds and stopping distance.

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Photo: Landing flare energy, from Eddie's notes.

Click photo for a larger image

Most aircraft use a VREF that is 1.3 times the stall speed, though some aircraft get as low as 1.23. You might think that 30 or 23 percent above stall speed is ample, but keep in mind the airplane has a downward vector which is aimed usually 3 degrees along the acceleration of gravity. You will need energy to stop that acceleration and that energy comes from your forward velocity. As you pull back on the yoke or stick, you are trading excess airspeed for a decreased downward vector.

Here's where it gets tricky. Your landing distance is more than likely based on touching down at VREF. Some manufacturers are explicit about this. Even though they want you to make the wind additive, they want you landing at VREF.

So let's say you do that. You are just a few feet off the ground at VREF and your negative gust hits. Now you have less energy to flare. Or lets say the positive gust hits. Now you are too fast for your landing data. What to do?

If I were writing the manual, I would recommend using half the headwind component plus all the gust, and then I would base my landing distance performance number on the highest possible touchdown speed. My AFM only provides for a 10 knot additive when computing landing distances and in a typical scenario that adds between 15 and 25 percent to my landing distance. If I know my required landing distance is more than 3/4 of the available runway, I know I will have to worry about the gust additive and perhaps find someplace else to land.

Eddie

PANS OPS versus TERPS?

You know that when the approach plate says "PANS OPS" you aren't going to be flying a classic U.S. procedure turn the way you learned in the U.S. during instrument flight training. But sometimes when you are in a foreign country you see "TERPS" on the approach plate. Now what?

More about this: Course Reversals.

Dear Eddie,

My particular question is in regards to ICAO procedures. In general in the US we use FAA procedures and in non US areas use ICAO procedures. So at a field like Bagram in Afghanistan what procedures are actually in place when you fly a full procedure, ICAO or FAA? It seems unclear, most people I ask aren’t entirely sure and have flown in and out of there countless times which means clearly it isn’t that big a deal which isn't the best argument when flying expensive aircraft. So Bagram it would appear was TERPS'd by the US I would think yet it is a foreign country who has their own AIP but on the surface since FAA and ICAO use different TERPS criteria it would make sense to fly it based on who TERPS'd it. Either way it’s extremely confusing because there are good arguments to use FAA procedures and good arguments to use ICAO procedures so what is the correct answer?

Signed, R. Fader
Fort Lee, New Jersey

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Photo: Bagram, Afghanistan (OAIX) ILS or LOC DME Rwy 03R, Jeppesen 11-1, 15 Jun 18

Click photo for a larger image

Mister Fader,

You are quite right, it is confusing. When I was in the Air Force we taught that seeing "TERPS" on the approach plate meant you flew U.S. procedures, period. We believed there were two choices: TERPS and PANS OPS. But it is more complicated than that.

Bagram does indeed say TERPS on the chart and given that most of the traffic in and out of there is the U.S. military, I think flying a TERPS procedure entry would be a safe bet. In countries where the U.S. has a strong presence, the answer can be airport specific. Take a look at two airports in Germany, for example.

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Photo: Ramstein, Germany (ETAR) ILS or LOC Rwy 08, Jeppesen 11-1, 17 Nov 17

Click photo for a larger image

Ramstein Air Base is a U.S. Air Force installation which primarily serves U.S. aircraft. The place on the chart we are used to seeing TERPS says "MIPS" which means "Military Instrument Procedures Standardization." MIPS is taken from a NATO supplement to ICAO Document 8168-OPS/611 Volume II. Confused? Well fly a little further east . . .

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Photo: Munich, Germany (EDDM) ILS or LOC Rwy 08L, Jeppesen 11-1, 26 Oct 18

Click photo for a larger image

So in the same country you have two different approach types. The German AIP is silent on this subject which leads you to believe everything, everywhere is in accordance with PANS OPS and you will be entering the procedures in accordance with ICAO Doc 8168. But there is an agreement in place between Germany and the U.S. military that provides an exception. The only place we civilians can see that in writing is in the Jeppesen ATC pages for Germany, which state:

[Jeppesen Airways Manual, ATC, Europe, Germany] Instrument approach procedures for civil airports are based on the PANS-OPS, Document 8168. Instrument approach procedures for military aerodromes are based on the United States Standards for Terminal Procedures (TERPS) or based on Military Instrument Procedure Standardization (MIPS).

I imagine there is a similar agreement with Afghanistan but I haven't seen it anywhere. Jeppesen has this:

[Jeppesen Airways Manual, ATC, Middle East, Afghanistan] Instrument approach procedures are based on the United States Standards for Terminal Procedures (TERPS) and on the PANS-OPS, Document 8168.

The word "and" is a bit misleading: is it TERPS or PANS-OPS? Your approach says TERPS and I think that is a good assumption. I agree with you that it makes sense to fly U.S. TERPS procedures when flying an approach procedure that says that. But you have a leg up in that you seem to understand both. So if you are about to start a course reversal which is depicted as a procedure turn (or the other way around) and the TERPS answer is different than the PANS OPS answer, I would simply ask. “We are about to turn right to begin the procedure turn, does that check with your expectations?” The worst thing they can do to you is laugh and call you names. That is a small price to pay for clarity.

Plotting the Hawaii "Romeo" Routes?

More about this: Plotting 101

Dear Eddie,

Please settle a bet for us. We fly from California to Hawaii almost every other week and have all the Romeo Routes memorized. We all agree that we need to plot over the North Atlantic because those tracks change twice a day. But the Hawaii tracks have been set in stone as long as any of us can remember. So we think there is no need to plot when flying the fixed tracks between California and Hawaii. And that also means we don’t have to do the ten-minute post position plot either. That’s right, isn’t it?”

Signed, R. Fader
Fort Lee, New Jersey

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Photo: Plotting Required, from 8900.1, Vol 4, Ch 1, ¶4-80

Click photo for a larger image

Mister Fader

No, that’s not right. Just because the route doesn't change on a daily basis doesn't mean you or your FMS will not make mistakes. The distance between ground-based navigation aids between California and Hawaii far exceeds those required by FAA Order 8900.1, Volume 4, Chapter 1, Paragraph 4-80.A, which says you must plot.

What the regulation says is that, “Plotting procedures are required for all turbojet operations where the route segment between the operational service volume of ICAO standard ground-based navigational aids exceeds 725 NM.” If you are flying a turboprop, the distance decreases to 450 nautical miles.”

So what is the service volume on an ICAO standard ground-based navigational aid? Depending on your altitude, that can be anywhere from only 25 nautical miles for an NDB or up to 130 nautical miles for a VOR.

So, as a rule of thumb, I’ve always plotted if I was further than 800 nautical miles from the nearest usable VOR.

That same regulation, by the way, also specifies the 10-minute post position plot, so the same rule applies. You do need to do a post position plot.

Eddie

References

14 CFR 97, Title 14: Aeronautics and Space, Standard Instrument Procedures, Federal Aviation Administration, Department of Transportation

14 CFR 97.3 Interpretation, AFS-400, 2013

Aeronautical Information Manual

Air Force Manual (AFM) 51-37, Instrument Flying, 1 December 1976

Air Force Manual (AFM) 51-40, Air Navigation, Flying Training, 1 July 1973

Boeing 737 NG Flight Crew Training Manual, Revision 12, June 30, 2013

Dassault Falcon 900X Crew Operational Documentation for Dassault non EASy (CODDE), Original, March 26, 2010.

FAA-H-8083-15, Instrument Flying Handbook, U.S. Department of Transportation, Flight Standards Service, 2001.

FAA Orders 8400 and 8900

Gulfstream G450 Airplane Flight Manual, Revision 35, April 18, 2013

ICAO Doc 8168 - Aircraft Operations - Vol I - Flight Procedures, Procedures for Air Navigation Services, International Civil Aviation Organization, 5th edition, 2006

United States Standard for Terminal Instrument Procedures (TERPS), Federal Aviation Administration 8260.3B CHG 25, 03/09/2012

Revision: 20190217
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