FAF to MAP Speeds

2nd505th

2nd505th

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2nd505th
My instructor insists I fly 90kts FAF to the MAP on an ILS or LOC approach. I calculate (hopefully correctly) that a standard ILS 200' AGL MAP puts me 3,816 feet from the threshold at 3 degrees. That is about the distance I think I would be on a base to final in a VFR traffic pattern and normally in my plane I would be at 68kts. 90 kts seems way to fast and its bugging me. Am I wrong here?
 
It's 100 knots in a Cirrus, plenty of time to get slowed down to land from minimums if you remember to chop the throttle. Cirrus wants no config changes below 500 feet AGL, so landings at minimums are usually at 50% flaps, 85 knots.
 
The typical instrument approach speed from the FAF to the MAP/DA is faster than your VFR approach speed on final. It's kind of a real world compromise, recognizing that if you flew 70 KIAS on an IAP on a real instrument approach, particularly to an airport with a decent amount of IFR traffic, you would be interfering with operations. At some, you might even spend a lot of time being vectored away and off the approach so others can get in. It's also the demarcation between category A and B minimums.

90 KIAS is very standard and completely safe in most any single I'm aware of (I've flown about 30 types; in some I use 105). I don't know a single in which it presents a landing problem - even a Mooney will slow down for landing at that speed - except perhaps a nonprecision approach to a very short field with high minimums, and even then I wouldn't be using 1.3 Vso.
 
OK. But I do notice that the time calcs for FAF to MAP include a timing for 60Kts.
 
Don’t have the answer but 90 knots is what I was taught to do in C172s and a Maule. After training, I’d go a little faster in some instances. It’s not too fast - anything slower seems slow to me.

Without me having checked the calcs, have you considered that in the VFR pattern you are aimed at the threshold but on an approach you are aiming for a touchdown zone that is further down the runway?

...and of course during training you will probably be doing more misses than actual landings, not that it should make any difference.


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So we're looking at this approach.

If it's ILS I think you do what you want and keep the needles centered. For LOC maybe he's trying to keep you on 90 so you don't have to interpolate the timing to the MAP? But also, you're still adding 1500' since you're not going to the numbers, you're going to markers. Should be plenty of time to slow down a 140.

[SGOTI talking - soon there will be CFII's to opine]
 

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My instructor and I, in my PA28-140, always did them at 90 knots as well (and that's what I now use, now that I have my IR)...what's wrong with 90 knots? It helps when you get to the bigger airports, and they are squeezing you in between bigger planes. 60 knots is S L O W!
 
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I fly at 90 knots in my Cherokee 140 on instrument approaches as well
 
Flying faster on the approach reduces your wind correction angles, keeps the aircraft at a more stable speed, gives you more energy on the missed approach, and more wiggle room from stall. I certainly wouldn't want to be IMC, at low altitude, near stall speed, getting bounced around by turbulence.
 
I was also taught 90 knots, and did that IFR training in an Archer and Skyhawk.

When actual IMC you will usually be one of the slower planes on the approach, even at 90 knots you're going to have jet and turboprop traffic and other higher performance aircraft gaining on you. As posted above you will also be in a much more stable configuration at 90 knots than you would be bouncing along at 65 knots

Have fun!
 
Keep in mind, if you elect a speed that is in Category B, then you have to use Category B minimums where they are higher than Category A. Also, when flying an ILS or LPV to RVR 2400, with prevailing visibility very low, The transition to normal landing speed can be unstable at the wrong time. VFR to a long runway at a busy airport, then a high speed is fine.
 
90 knots is a good speed for a Cherokee...there’s plenty of time to get the airplane slowed to land, and it has the stability and control advantages already mentioned, with the added bonus that it allows for increased operations at an airport...3 landings per hour is very minimal, and can result in a lot of people (including yourself) spending a lot of time holding. And yes, I’ve sat in a hold for over 20 minutes watching a 182 fly a 70-knot approach from start to finish. Never lost sight of him (the weather was reported 900 broken, but the clouds were closer to scattered), and I almost beat him to the ramp.

Bottom line, listen to your instructor on this one. ;) Like anything, it’s an acquired skill.
midlifeflyer said:
Absolutely no problem for a Cherokee coming into a 6000'+ runway.
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[soapbox]I would add that runway length shouldn’t factor into this...a pilot needs to be able to land the airplane in the appropriate portion of the runway or initiate the go around and/or missed approach. A significant portion of aircraft accidents (1/3 is the number I’m recalling) is runway excursions. One of the best ways to have a runway excursion is to “get used to” having more runway than you need, and when you finally need to put the airplane on the correct portion of the runway, not only can you not do it, you don’t even think about needing to do it. As an examiner, the most common reason I’ve had to fail an applicant (and I primarily deal with professional pilots) is a touchdown in excess of 3000 feet down the runway. While that’s not normally an issue for a Cherokee on a 6000-foot runway, it doesn’t take much runway contamination to more than double the stopping distance...if you fly into an airport that reports runway condition codes, an RCC of 5 (6 is dry, 0 is nil) can double your stopping distance.

Don’t be the next guy to slide off a runway. Touch down at the proper speed and in the proper place.[/soapbox]
 
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aterpster said:
Keep in mind, if you elect a speed that is in Category B, then you have to use Category B minimums where they are higher than Category A. Also, when flying an ILS or LPV to RVR 2400, with prevailing visibility very low, The transition to normal landing speed can be unstable at the wrong time. VFR to a long runway at a busy airport, then a high speed is fine.
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Good reminder there! Especially given that I tend to fly B speeds even in my old Maule. Mixing it up at a Class B airport, the approach was often the fasted part of my flight.

Doing a random and very brief look at a few plates, I’m reminded that differing Category speeds seem to mainly apply to non-precision approaches (?), which makes sense.

But in low visibility conditions there’s a lot to be said for stabilized flight.




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Yes we are not supposed to allow our procedures to be influenced by other traffic, but after you have flown a few ILSs at your 68kts in a busy airport, it will become apparent that you are hindering other traffic by moving along so slowly. Also, it is not going to be a huge difficulty to step it up a little bit, in fact the airplane will handle better with the extra speed (less wallowing). More comfortable deck angle too.
 
2nd505th said:
My instructor insists I fly 90kts FAF to the MAP on an ILS or LOC approach. I calculate (hopefully correctly) that a standard ILS 200' AGL MAP puts me 3,816 feet from the threshold at 3 degrees. That is about the distance I think I would be on a base to final in a VFR traffic pattern and normally in my plane I would be at 68kts. 90 kts seems way to fast and its bugging me. Am I wrong here?
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I am really bad at math, so check my accuracy.

Generally the glide slope has you crossing the threshold (TCH) ~50 feet AGL with the touch down zone about 500 ft from the threshold. So if your 3816 is correct, 3816+500 = 4300 feet or 7/10 NM from the MAP. At 90 knots, providing you maintain a GS of 90 kts to the ground, you have 47 seconds to apply full flaps, reduce the throttle and slow to touch down speed. In reality in a 140 with some headwind, you have about one minute do get the final flaps down, reduce the throttle and slow to touch down speed.
 
I’d also add that I doubt anybody would consider slowing 2 knots over 10 seconds to be “unstable”...if you really need to be at 68 knots by the time you spot the runway at 100 feet, that’s less than two minutes of VERY gradual slowdown...halfway from the FAF to the runway at 90 knots, then pull back 50 or 100 RPM and gradually slow to the new target speed.
 
2nd505th said:
OK. But I do notice that the time calcs for FAF to MAP include a timing for 60Kts.
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Don’t worry about the time calcs for the MAP, if you’re flying a ILS and you loose the glide slope for who know what’s reason, real world you’re going to go missed and figure out what happened, it would be silly to continue on a IAP that just had a major malfunction on ether your end or the ground end.

As for the speed, not that important as long as it’s stabilized and you can handle it.

If it’s a decent length runway, as most ILSs have, I’ll fly it at 120kts in my 185, one dot off the glide slope I’ll drop my gear, that’ll take me down a couple knots, keep it zero flap, break out, runway assured, power all the way back and add a flaps as needed
 
In a 140, you're Category B. That's what ATC expects you to fly unless you are unable to maintain speed. You configure for landing at the FAF and fly a stabilized approach all the way down. You should be able to acquire the landing environment before reaching minimums, and continue into ground effect, then hold the aircraft off till slowing to landing speed. This is how the approach is designed. Your CFI is correct.
 
James331 said:
... If it’s a decent length runway, as most ILSs have, I’ll fly it at 120kts in my 185, one dot off the glide slope I’ll drop my gear, that’ll take me down a couple knots...
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Your 185 has retracts?
 
wilkersk said:
In a 140, you're Category B. That's what ATC expects you to fly unless you are unable to maintain speed. You configure for landing at the FAF and fly a stabilized approach all the way down. You should be able to acquire the landing environment before reaching minimums, and continue into ground effect, then hold the aircraft off till slowing to landing speed. This is how the approach is designed. Your CFI is correct.
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Category B? You sure about that?

  • Category A: Speed 90 knots or less.
  • Category B: Between 91 and 120 knots.
  • Category C: Between 121 and 140 knots.
  • Category D: Between 141 knots and 165 knots.
  • Category E: Speed 166 knots or more.
 
Clip4 said:
Category B? You sure about that?

  • Category A: Speed 90 knots or less.
  • Category B: Between 91 and 120 knots.
  • Category C: Between 121 and 140 knots.
  • Category D: Between 141 knots and 165 knots.
  • Category E: Speed 166 knots or more.
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Argh!!!! You got me. Shoulda looked at an approach plate. I just remember 90kts/landing configuration/stable approach getting hammered in by my CFI.
 
90 knots GS will equate to 500fpm descent rate on the glideslope, which gives you nice, easy to see numbers on the steam gauges. Modern avionics have tick marks, but the same idea applies. Holding a steady ground speed allows you to back up your ILS with a timed approach to LOC minima in case you have a glideslope failure.

I personally prefer a stepped approach with gradual deductions with marker passage, gear and flap application, but I never go slower than 90 KIAS.
 
I'd like to be at the FAF at a speed that permits a landing configuration. That means for the Navion to be at 100 MPH (87 knots). You can't lower the flaps/gear faster
 
flyingron said:
I'd like to be at the FAF at a speed that permits a landing configuration. That means for the Navion to be at 100 MPH (87 knots). You can't lower the flaps/gear faster
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"Gear down to go down" is my SOP, so gear extension speed a limiting factor for me too. I use flaps for approaches pretty rarely, except in a small minority of the airplanes I've flown.
 
2nd505th said:
OK. But I do notice that the time calcs for FAF to MAP include a timing for 60Kts.
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I would argue that 60 kts isnt safe in IMC on an approach.....the plane is far less controllable and any turbulence encountered is more likely to result in an inadvertent stall, which is messy when you are in IMC close to the ground. In addition, flying a decelerating approach in IMC is even worse, as you are constantly having to reconfigure the plane.....power and pitch are constantly changing. 90 kts is a perfectly good speed for a typical piston single.
 
Time and place for everything. There are times you need to be able to shoot an ILS at best forward speed. If you’re number one going into a sleepy airport, there’s no need to rush things.
 
kgruber said:
What is required for a FAA checkride is different than what is necessary to be an competent instrument pilot, able to negotiate saturated airspace.
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Based on the many discussions of the subject I've seen, I think there is a definition problem. Mostly the FAA's doing, but some our very own in leading us to believe that anything which varies means unstable. So I wonder whether your disagreement with @Walboy is all about definition. Take the ACS guideline he quoted, with my highlight:
Walboy said:
"Maintain a stabilized final approach from the Final Approach Fix (FAF) to DA/DH allowing no more than ¾-scale deflection of either the vertical or lateral guidance indications and maintain the desired airspeed ±10 knots."
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I don't think "desiring" to use a step-down airspeed on an approach, such as maintaining 100 KTS until 1000 AGL and then slowing to 85 means you are unstable. OTOH, if having decided on those speeds, good airmanship means you are able to maintain it. Fluctuate all over the place, you are unstable.
 
midlifeflyer said:
Based on the many discussions of the subject I've seen, I think there is a definition problem. Mostly the FAA's doing, but some our very own in leading us to believe that anything which varies means unstable. So I wonder whether your disagreement with @Walboy is all about definition. Take the ACS guideline he quoted, with my highlight:


I don't think "desiring" to use a step-down airspeed on an approach, such as maintaining 100 KTS until 1000 AGL and then slowing to 85 means you are unstable. OTOH, if having decided on those speeds, good airmanship means you are able to maintain it. Fluctuate all over the place, you are unstable.
Click to expand...

I thought kgruber was kidding, even in a 140 full throttle on descent will probably result in 180 knots if it goes on long enough.
 
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