How fast do you fly an instrument appch?

[Joseph II]

In a Cessna 172?

I was taught to fly at 90kts, but more and more pilots I've spoken with say fly at 70, 75, or at most 80kts.

My argument was when training out of West Chicago, IL you couldn't take your own sweet time flying down the ILS, they wanted you out of the way. The "slow approach" pilots said don't worry about the planes behind you.

What do you think?

 

[flydog]

This will vary but at most 121 and 135 Flight Departments the SOPs call for being in a stabilized approach by the outer marker or 1000' if you are shooting an approach under IMC conditions. This is usually Vap +/- 10. If its a visual or ILS during VMC our SOP calls for being stabilized by 500'

If its VFR and you are going into a busy airport like BOS or SFO then its true that ATC will generally want you to hustle to the marker and will usually tell you "200 knots to the marker" or something to that effect. Even in IMC conditions they can ask you to keep your speed up within safe parameters. Keep in mind traffic is being fed into the approach controller at 250 kts and if you slow to 140 kts for an approach you will be stacking up a lot of traffic.

I think most of use that fly jets will usually slow to Vle and keep the gear and full flaps up until the marker. This usually gives an extra 40-50 knots for ATC to play with and still allows for a stabilized approach.

If you are in a 172 or any Cat A airplane I probably wouldnt worry too much about it. I dont think the difference between 75 and 90 knots is really going to clear any airspace. You can fly the ILS at 120 knots if you are comfortable but ATC doesnt expect that and the main thing is that your are stabilized

 

[Tim47SIP]

I think you answered your own question. We are constantly told to keep the speed up going into Atlanta because of traffic. Do what you are comfortable with, it is safer that way!.

 

[TWA Dude]

They're all correct. I remember in instrument training starting out an ILS at 120kias just to show it could be done. You should fly what's comfortable for you but you should also do your best to fit into the system. The higher the ceiling/vis generally the faster approach speed you can use.

Note that I'm not advocating abandoning the stabilized approach concept. But let's face it, for a 172 it's primarily a training tool. In the MD80 we can get away with just about anything as long as we're stabilized by 500 agl, and I've seen that limit pushed by a wide margin.

I recommend you try it as various different speeds so you can know what your comfort limits are. Have fun!

 

[Green Banana]

If you are renting the aircraft, as fast as you can.
If you are being paid by the hour,, as slow as you can.

 

[bobbysamd]

Instrument approach speed

Go read your IAP legend. Something like at least 1.3 Vso at maximum gross for your airplane. Probably that's where your hearing people telling you to fly it at 80 kts, etc. My instructor taught me 100 mph (90 kts) and no flaps til short final in the '70s model 172 in which I learned to fly.

I agree with flying it as fast as you're comfortable so you don't slow down the heavy whose following you, bearing in mind you have to slow down enough to throw out flaps, etc.

 

[generaltso]

I got in to a discussion with a very experienced CFI about this. I was telling my students to fly slower to make the approach easier, but this CFI insisted that the faster you fly the easier the approach would be.

Anyone want to comment on this?

I thought the slower you are the slower the deviations will be therefore you will have more time to catch them and correct them.

He says the faster you go the more effect changes will have on reintercepting the course.

I can see validity in both arguments, but for me a slower approach feels easier.

 

[bobbysamd]

Faster v. slower

I agree with your CFI friend. Try it in the sim. Try flying the same old DAB ILS you've flown for years at 90 kts at 150 kts. Now, things will happen faster but you will need fewer and smaller corrections.

It stands to reason, because you will have less of a crosswind component to deal with. Also, the higher speed seems to make the airplane more stable.

Just try it in the sim lab. While you're at it, try flying the DME arc part of the approach at 150 kts or as fast as you can make the sim fly.

Good way to prepare for "the interview," too, by the way.

 

[Timebuilder]

In a 172, I used 90 kts for trainees. It's a speed (groundspeed) that shows a printed time on the chart for the missed, it's not so fast that a new student will let a deviation go "full scale" very quickly, and it easily gets the job done for the student, allowing for several aproaches during the lesson. At our little class D field, we didn't have much trouble with traffic coming up behind us.

When I would take a student into actual and shoot an appraoch into PHL, that was another story. Invariably, the controller would ask me to "keep the speed up for a 767, ten miles in trail...." while clearing me to intercept the localizer. In that situation, I'd show the student the power-on descent for the ILS, and fly at about 130 kts until I have the runway, then slow to 110 kts for the flaps 10, go full flaps in the arc, and land.

Certainly, the sim is a great place to experiment, and cheap, too. Remember, many DE's and inspectors are coming to a checkride expecting you to do everything pretty much the same way as everyone else does: speeds, hold entries, and the like. If the ride is your near-term goal, then fly it like your instructor tells you is the standard way. He probably knows what the local "king" expects to see in his "kingdom".

 

[Mickey]

If it's good weather, then a fast approach is just fine, however, if it's 100ft/ 1/2 mile then I think the stabilized approach at a realistic speed makes more sense. Usually your final landing(ref) speed plus 10kts works fine. Keep in mind when instructing the purpose is to teach the person to be able to fly to minimums safely on their own, down the road. If they think the 'norm' is to fly the approaches fast then they are only making life more difficult for them when they really need to get in. Remember the purpose of an approach is to be able to land at the end of it. I've seen a lot of people fly their approaches in C172Rs at 90kts. with 0 flaps, at 200AGL I would say look up and land. It's amazing how manky of them would add the flaps and balloon up 100ft. and ruin the whole stabilized concept. If they were in older C172s I would remind them that 90kts. is above Vfe.
As far as which is easier, fast or slow. If you are flying slow you have more time to correct for an incorrect input and more time to realize that you have an incorect input in. Ask at CATII pilot if they like to fly their approaches 40-50 kts. fast. I think the point I'm trying to make is that when it really counts, you should be at the proper approach speed for a safe landing. When there is good weather it is okay to keep the speed up to help the people behind you.







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