Which approach category minimums to select (flying faster than your plane's category)?

[robertb]

Hello,
I have a buddy working on his IR and would like clarification from CFIIs or others in the know on here. As I understand it, if I fly my Cessna 182 at 110 knots down the final approach coarse all the way to the runway, I would select the category B minimums... and float and float and float. But, at what point do I need to be at 90 knots in order to use the category A mins? When I got my IR twenty years ago, I think we flew 90kts pretty much the entire approach but I can't recall. Flying the approach from the IAF all the way in at 90 knots seems a bit unnecessary and even from the FAF to the runway seems a bit much. I have a couple of guesses to the answer but don't want to embarrass myself.

Thanks in advance gang!

 

[MauleSkinner]

Ultimately, before you operate below Cat B altitude or visibility.

 

[Tantalum]

Letter of the law: 97.3 defines category based on "based on a speed of VREF, if specified, or if VREF is not specified, 1.3 Vso at the maximum certificated landing weight." so you can't really change your aircraft category simply by choosing to fly it faster

Real world: the 'category' becomes more and more critical the closer you get to minimums of cat B, cat A, etc. If you hit the cat B minimums you can't really transition to cat A and say you're doing things "right".. but if you're 5 miles out and tower says 'keep your speed up for traffic' that's less of an issue (assuming you're obeying the altitude restrictions) than having an incorrect speed as you near the respective MAP or DH

How I was taught: at the FAF you are at your approach speed, IE 90 knots, with one notch of flaps, and gear down. Fly that all the way down.

 

[MauleSkinner]

so you can't really change your aircraft category simply by choosing to fly it faster

According to the IPH, “If it is necessary to operate at a speed in excess of the upper limit of the speed range for an aircraft’s category, the minimums for the higher category must be used.”

 

[Tantalum]

According to the IPH, “If it is necessary to operate at a speed in excess of the upper limit of the speed range for an aircraft’s category, the minimums for the higher category must be used.”

Thanks, which makes sense if you think about.

 

[robertb]

Thanks for the info gentlemen! I'll take a gander at the IPH. I'll need to first find it and then knock about 20 years of dust off of it.

 

[robertb]

According to the IPH, “If it is necessary to operate at a speed in excess of the upper limit of the speed range for an aircraft’s category, the minimums for the higher category must be used.”

My question will be: "higher category must be used"... until when? From when you were going fast enough to need the higher category mins or can you revert back to the lower mins further along if airspeed is to a lower category? It would seem odd to switch back and forth but, from a practical POV, it seems logical as long as you remain stabilized.

 

[Dave Theisen]

You are bound to the minimums based on the speed you are flying. Think of it in terms of circling approaches. The radius of protected airspace increases as speed increases. If you are flying to minimums based on your aircraft category but flying a significantly higher speed, you may stray outside of the visibility minimums and obstacle protection.

 

[MauleSkinner]

My question will be: "higher category must be used"... until when? From when you were going fast enough to need the higher category mins or can you revert back to the lower mins further along if airspeed is to a lower category? It would seem odd to switch back and forth but, from a practical POV, it seems logical as long as you remain stabilized.

Say you want to keep your speed up for following traffic, so you’re flying 125 KIAS…you need to honor Cat C minimums since you’re above 120 KIAS.

As you approach minimums, you slow to your normal 85 KIAS, so you can continue down to Cat A minimums.

 

[robertb]

Say you want to keep your speed up for following traffic, so you’re flying 125 KIAS…you need to honor Cat C minimums since you’re above 120 KIAS.

As you approach minimums, you slow to your normal 85 KIAS, so you can continue down to Cat A minimums.

That makes sense. I like the way you initially phrased it, "before you operate below Cat B altitude or visibility".

 

[midlifeflyer]

Approach category is based on Vref. 1.3 Vso if a Vref is not published.

Thanks for the info gentlemen! I'll take a gander at the IPH. I'll need to first find it and then knock about 20 years of dust off of it.

Same language appears in the AIM at 5-4-7. Both are available online. The IPH is one of the best instrument procedure references available.

 

[Let'sgoflying!]

Thanks for the info gentlemen! I'll take a gander at the IPH. I'll need to first find it and then knock about 20 years of dust off of it.

direct pdf download:

https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/instrument_procedures_handbook/FAA-H-8083-16B.pdf

 

[John Collins]

I would say you have to be at the lower speed category before you reach the higher speed category minimums or you would have busted minimums. As a practical matter, it makes sense to me that you should be stabilized at the speed no later than the FAF inbound. The intermediate leg is intended to be the leg where you get configured and stabilized for the final approach descent, so it is where I would target to be on speed. This is from the TERPS general information:

2-5-1. Intermediate Approach Segment. This is the segment which blends the initial approach segment into the final approach segment. It is the segment in which aircraft configuration, speed, and positioning adjustments are made for entry into the final approach segment.

 

[MauleSkinner]

Same language appears in the AIM at 5-4-7.

I know the AIM “isn’t regulatory but,” but does compliance with approach categories have an actual regulatory track via Part 91 requiring compliance with Part 97 approaches, or anything like that?

 

[John Collins]

I know the AIM “isn’t regulatory but,” but does compliance with approach categories have an actual regulatory track via Part 91 requiring compliance with Part 97 approaches, or anything like that?

Similar wording appears in the TPP document. However, they do use the word "should" which indicates it is not strictly regulatory.

An aircraft shall fit in only one category. When necessary to operate the aircraft at an airspeed in excess of the maximum airspeed of its certified aircraft approach category, pilots should use the applicable higher category minima.

Although this appears to be a recommendation, since it is intended to ensure the aircraft remains within protected airspace, the self correcting effect on the gene pool will over time reduce the number of repeat offenders.

 

[Velocity173]

Obviously if you’re going to shoot the whole approach to MDA / DA you would use the higher mins if flying in those Cat speeds. I don’t know if there’s a specific point on the approach you have to be at in order to use the lower mins if you slow down during the approach.

I can tell you this, in helicopters you can fly the highest speed in the mins section but in order to apply the visability reduction that’s allowed for Cat A, you gotta be at Cat A speeds (90) before reaching the MAP.

 

[schmookeeg]

You didn't ask this, and I suspect this is already your mindset, but on an approach where the category minimums matter, nfw do I want to be changing my speeds and configuration. Pick one and stick to it from IAF to breakout. You've got enough to do without using brain CPU to choose some new cooler speed to fly.

I find Cat B easier than Cat A in the planes I fly, but I imagine this is very airframe specific.

 

[Martin Pauly]

You didn't ask this, and I suspect this is already your mindset, but on an approach where the category minimums matter, nfw do I want to be changing my speeds and configuration. Pick one and stick to it from IAF to breakout. You've got enough to do without using brain CPU to choose some new cooler speed to fly.

That's a good general rule. Having said that, there is the occasional case where ATC asks the airplane for a higher-than-normal approach speed. With some practice, this can be accommodated safely, even in IMC - easier in some airplanes than others (e.g. a Cirrus can take a long time to slow down from 150 KIAS while descending on the glideslope).

For anyone who hasn't practiced this or is not 100% comfortable, I agree with @schmookeeg : fly the approach at the speed you are used to. Being on speed is part of the stabilized approach criteria.

- Martin

 

[midlifeflyer]

I know the AIM “isn’t regulatory but,” but does compliance with approach categories have an actual regulatory track via Part 91 requiring compliance with Part 97 approaches, or anything like that?

i agree with @John Collins' comment. It's not "regulatory" in the sense of a specific pilot-mandatory regulation like 91.175. More "must" if you want to have the terrain and obstacle clearance TERPS design criteria provides.

 

[midlifeflyer]

Pick one and stick to it from IAF to breakout

At least from FAF to breakout. As @Martin Pauly pointed out, keeping speed up to the FAF is a common procedure at busier towered airports (my first was 120 in a 172 ). Then there are procedures where the IAF is some distance away from the rest of the action. If your approach speed is 90, there's no real need to fly it for a 15 mile IAF to FAF.

 

[NealRomeoGolf]

At least from FAF to breakout. As @Martin Pauly pointed out, keeping speed up to the FAF is a common procedure at busier towered airports (my first was 120 in a 172 ). Then there are procedures where the IAF is some distance away from the rest of the action. If your approach speed is 90, there's no real need to fly it for a 15 mile IAF to FAF.

My home airport is a 10 mile leg between IAF and FAF. I'm with you. There's no way I'm doing 100 the whole way. I do 120 until right before the FAF, drop the gear, which slows me to 100 and then cut my MAP to 15 and mosey down the glideslope.

 

[midlifeflyer]

My home airport is a 10 mile leg between IAF and FAF. I'm with you. There's no way I'm doing 100 the whole way. I do 120 until right before the FAF, drop the gear, which slows me to 100 and then cut my MAP to 15 and mosey down the glideslope.

Plus, think of the pitch-power-configuration knowledge for your airplane that demonstrates!

 

[MauleSkinner]

I once got to sit in a hold for over 20 minutes while watching the guy who got to the VOR first shoot his approach…70 knots for the whole procedure, I’d bet.

I didn’t beat him to the ramp, but I beat him to the FBO.

 

[RussR]

From a TERPS perspective, approach category only has a role in a very few calculations.

1. Any time a turn is involved. Obviously, faster airplanes have a larger turn radius.
a. This is why Circling Radii, and therefore usually Circling MDA, are larger/higher for higher Cat airplanes. This is the most typical and obvious effect of aircraft speed.
b. If there is a turning missed approach, sometimes the larger turn radius of the higher Cats picks up more obstacles that a lower speed/Cat would turn well inside of. This can cause the higher Cats to have a higher DA/MDA. But although this provision is in the books, this is very rarely seen in the wild. Example - TRM RNAV (GPS) RWY 35, which has Cat C/D MDA 500 ft higher than A/B, specifically because of the wider turn radius and the terrain to the NE.

2. Visibility values. There is no TERPS calculation at work here, it's (almost always) a simple look-up table of HAT/HAA vs Cat. Rationale? Probably simply because the faster you're going, the less time you have to see things and react.

So, from a TERPS perspective, it only really matters that you're at the appropriate Cat speed by the time you want to/need to either maneuver, or see the runway.

If you come down final at 150 knots in your 172, as long as you're at or below 90 knots by the time you reach DA/MDA and go visual, or begin a circling maneuver, or begin a missed approach turn, you can fly the Cat A minimums and be assured of obstacle clearance. Not the best idea from a stabilized approach standpoint, but good enough for TERPS.