Downwind to base to final

[nikcht]

Hi all, I'm a long time reader of the forum and just decided to register. Please feel free to move this topic if it isn't in the right place.

I am a student pilot with 10 hours of experience. I do all my flying in a 172S.
Recently, my instructor signed me off to be able to do solo circuits (at 7 hours). I noticed that I am having some trouble flying the appropriate airspeeds.

My FTU suggests the following: on downwind 95 kts @ 10 degree flaps. Base @ 70 kts and 20 degree flaps. Final @ 61 kts with 30 degree flaps, crosswind permiting.

Anywho, I find myself flying perfectly on downwind, however when I abeam the threshold, everything goes downhill. Once I abeam the threshold, I reduce power (to 1500) and wait until the air speed is well within the white arc and then drop flaps to 20 (usually around 78 knots is when I lower flaps). Once airspeed decreases to 70, I trim it out and start my descending turn to base. On base I am finding myself 90% of the time too high and too fast resulting in a poorly flown final, which in turn results in a poor landing.

I make a forward slip and fly the appropriate approach profile. But I was just wondering if there are any tips/tricks to have a well controlled and smooth turn from downwind to base to final? I asked my instructor and he said that I need to make sure that the aircraft is properly trimmed. I am certain it is! But maybe somebody can help me out with any personal tips or tricks?


Thanks

[mathias_now]

Hi Nikchat,

First of all congrats on the decision to learn to fly. Although I only have a few hours on the S model I found it flys much the same as the M or N models - After all it is a 172 so I will share the recipe my instructor taught me when I was first starting out.

When you're flying the downwind there is really no one speed at which you can fly it, but typically 2100-2200RPM works fine. When abeam the threshold pull the power back to 1700RPM and give the trim wheel three full shots nose up. 1700RPM and three shots of trim should give you around 70Kts, while holding circuit altitude. Once you have that stabilized, add 10 degrees of flaps. By that time you should be a about 45 degrees from the threshold (when viewed from the pilots window on the downwind) at which time you should pull the power to 1500RPM and start your base turn. When on base add another 10 degrees of flaps, which will give you a 300' per minute decent, and 65Kts. After you stabilize that and you turn final, at around 500-600' above ground, add the remaining 10 degrees of flaps. Short final with full flaps you should be around 55-60kts. Maintaining the proper sight picture at this point is very important, and power and pitch adjustments will likely have to be made since this is only a recipe. Trim is your friend. Dont focusing on the threshold or touchdown point alone. When you cross the threshold and transition to level, to slow your descent rate, the power should come to idle. Pulling the power to idle can be very distracting to some at first, and some people land with partial power instead. I would advise against this when starting out, since pulling the power allows you to bleed of some of that extra airspeed, which will ensure that you don't become airborne again once the wheels touch. Pulling power and not adding power, if needed, could also put you in a tough spot though. Up until around 20 hours I thought that I had to touch down at 55-60kts, man did I have some interesting landings back then..... The way I remember the transition from descent to landing is Level, Settle, and flare.

Hope this helps

MN

[AEROBAT]

Nikcht,

No one else is chiming in so I will give my 2 cents. I assume you are doing continuous circuits, one after the other. Adjust your timing on reducing your power to achieve the perfect approach. If you do the same thing every time you will achieve the same result.

Coming in a bit high and having to loose alt. is better than dragging it in adding power to make the field [that is my opinion and I am sure someone will dispute it]

Do you practice landing with no flaps or half flaps?

[dieselbro]

For what it is worth, and by no means am I suggesting that this is the correct method for everyone, this is how I was taught. Flying downwind was never done with flaps in a 172 (a twin-engine Seneca however yes the flaps would be at 10*, but that is a whole other ball game) but rather a power setting, be it 2300 RPM or slightly lower if there is more traffic in the circuit. Also I was taught to land with flaps, without flaps, or even partial flaps, it doesn't matter it can be done either way.

Once the touchdown point (numbers, first hash mark after the numbers, or whatever you have chosen) crosses 45* over your shoulder I would 1) Throttle to idle, slowly and gently of course 2) Turn base 3) Trim, about 3-4 times works out to be 70kts 4) Watch your airspeed, I was taught never to descend below circuit altitude until the speed stabilized at your approach speed of 70kts

Next while flying the base leg imagine a window that is where you turn final, this should be 500 AGL (or half circuit height). Monitor your altitude to see if you will 'fly' through that window at the target height of 500 AGL (half circuit height). Another thing to monitor would be your point of zero movement which if things are going well should be your touchdown point or slightly before it. These clues will let you know if you are too high or low.

Then I would make my turn to final. Keeping a good look outside and cross checking that picture with airspeed and altitude. Coming in to land is the same as it would be, watch outside towards the end of the runway, level off, bleed off airspeed, flare, touchdown.

NOW I do realize that you might want to use flaps on your landings. What would be different for me is on the initial turn to base after reducing power to about 1500 RPM or so and trimming for 60kts, I would wait until my airspeed got in the white arc and then drop 10* of flaps. While flying the base leg I would bring in 20* of flaps, and then turning final is where I would add 30* of flaps. Everything else would be the same, except the attitude you would see when looking outside during the approach would be different due to having the flaps deployed causing you to be pitched downwards more. Keep in mind the aids that you can use, such as the imaginary 'window' of what altitude you should be at when turning final as well as your point of zero movement with regards to your touchdown zone. So if your touchdown zone is moving up in your windscreen you will need to add power or lessen your descent, if the touchdown point is moving down your windscreen it means you will be high so reduce power to descend quicker.

Hope this helps, it was rather longwinded, and also keep in mind there are many ways to fly a circuit in a 172, this is simply my method. Also as AEROBAT mentioned alter when you reduce power to help fly your approach better.

[Cat Driver]

If you plan on maintaining a constant descent rate and attitude to your flare point and you want to fare so as to be at two feet above the runway at the completion of the flare, how do you judge two feet above the runway by looking at the far end of the runway?

[iflyforpie]

I don't really have any specific advice, but some general advice that might help you.

When you are descending and find you have excessive airspeed and altitude, first get back on airspeed then worry about altitude. If you are trying to correct your altitude by pushing forward, your plane will simply speed up and get there sooner, still giving you a steep approach. This is why setting your power and trimming the plane are so important. Once this is done, the plane will maintain its proper speed almost by itself. Then you use power to control your altitude.

About power. Most pilots don't know this, but often feel its effects as they rear their ugly heads in the worst situations. When increasing power, your trimmed speed decreases, when decreasing power, your trimmed speed increases. This is why if you find yourself low and slow with full flaps, it takes a cruise power setting and typically quite a bit forward pressure to maintain speed and reduce descent rate (this is very apparent in an overshoot on most planes). When you are high and fast, it takes reducing power to idle and a bit of back pressure (not very instinctive) to maintain your approach speed while you wait for the aircraft to increase descent rate. Of course, you can avoid lots of this by trying to keep power changes to a minimum.


If you find yourself coming in consistently high, I would suggest extending your downwind a bit and perhaps squaring off your base. Sometimes it is just crowding the field that is the problem.

But just remember, proper airspeed first (don't chase it, attitude, trim, and verify with the indicator), then altitude.

[dieselbro]

If you plan on maintaining a constant descent rate and attitude to your flare point and you want to fare so as to be at two feet above the runway at the completion of the flare, how do you judge two feet above the runway by looking at the far end of the runway?

I believe this was directed at me, so I will answer. It seems in my haste to make a reply to the OP that I may have skimmed over some things. Also because the OP was not asking for help on judging the flare. However I will try to put this in words. There is more to it then just looking at the far end of the runway, it also involves using your peripheral vision looking out the side to judge height. Also by using a differnt judgement point when you get closer to the runway. I transition to this after flying into my initial point at about 20 feet or so when it seems like you are going to 'crash' (for lack of a better word) into it. A good judgement IMO are the runway hash marks that are roughly a 100m in front of you. Because the human eye is better able to judge depth by objects that are closer to us. But you cannot look too closely because that all seems blurred to our eyes at the speeds we are moving at during this phase of flight. When you slowly begin to flare pay attention to this spot a 100m in front of the plane because our eyes can then use the far end, our spot, and the near end to figure out depth.

Okay, that probably was not the best explanation and I'm sure you have some input regarding this. Anyways hope this clears things up. And Cat Driver by any means post your explanation because I'm sure it will be better than mine!

[gustind]

Anywho, I find myself flying perfectly on downwind, however when I abeam the threshold, everything goes downhill. Once I abeam the threshold, I reduce power (to 1500) and wait until the air speed is well within the white arc and then drop flaps to 20 (usually around 78 knots is when I lower flaps). Once airspeed decreases to 70, I trim it out and start my descending turn to base. On base I am finding myself 90% of the time too high and too fast resulting in a poorly flown final, which in turn results in a poor landing.

If you are trimming properly as you've said, you are simply turning base a bit too early in which your case is when you get to 70 knots instead of when the threshold is 45 degrees to the aircraft. That being said, if you are configuring the aircraft for base right abeam the numbers, wait another 2 to 3 moments then start configuring the aircraft. When you're done, turn your head and you should be around that 45 degree mark. After that continue doing as you were taught....except I think it's 65 on final with 61 over the threshold .

Don't be afraid to ask any of your senior instructors for advice as well.

[Cat Driver]

Dieselbro, thanks for your answer as it was well thought out.

Some years ago I wrote an article for Pprune that explained in depth where to look during the three segments of a landing...the approach, the flare and the hold off portions.

The least understood portion of The landing among a lot of pilots is the last part..the hold off or the touch down portion.

For that portion of the landing ones center of focus should be at the point on the runway where apparent movement ceases...( about five hundred feet in front of the airplane for light aircraft with a hold off speed under 100 knots. )

Some day I may take the time to re- write that article, but I am not that motivated these days.

[Cat Driver]

Dieselbro, thanks for your answer as it was well thought out.

Some years ago I wrote an article for Pprune that explained in depth where to look during the three segments of a landing...the approach, the flare and the hold off portions.

The least understood portion of The landing among a lot of pilots is the last part..the hold off or the touch down portion.

For that portion of the landing ones center of focus should be at the point on the runway where apparent movement ceases...( about five hundred feet in front of the airplane for light aircraft with a hold off speed under 100 knots. )

Some day I may take the time to re- write that article, but I am not that motivated these days.

[KK7]

Hi nikcht,

I think ultimately this is a question that is reserved for your instructor, and you'll get a better answer from someone who is sitting with you in the plane and can see exactly what you're doing. But if I attempt to answer your question, I would say I suspect you are worrying about airspeed too much, and should focus more on the aircraft's attitude. In general I find if people are so focused on the airspeed, they have trouble controlling it, whereas if they simply set the desired attitude for the plane and disregard the airspeed, the airspeed turns out to be dead on.

Try doing some circuits and take note of the aircraft's attitude for each segment, whether it be the part along the downwind when you slow down, to the attitude you have on base to the attitude you have on final, right through to the attitude you need to flare and hold off. Attitude is key.

Once you get a good feel for the basic attitude the aircraft needs, you can make small adjustments on the approach. Given a proper safe approach profile (ie not dragging it in or being very high), you can make small adjustments using pitch to adjust the airspeed, and power to control the rate of descent.

[nikcht]

Do you practice landing with no flaps or half flaps?

Yes, I practice no flap / partial flap landings but not as often as full flap.

And many thanks to everybody who responded, your help is much appreciated

Now that I think of it, gustind is correct. I do turn my base earlier than I should resulting in the "Oh crap I'm too high" reaction. Instinctively I reduce power to increase my descent, but if I still find myself too high I act on instinct and pitch down, which would explain my high airspeed.

I will definitely try all the tips and trick you guys have suggested, and hopefully I will remember what iflyforpie said "airspeed first, altitude second"

I will keep you updated on how my next lesson goes

And to Cat: I find that when I fly the appropriate approach profile, with proper airspeeds and altitudes, my flare and landing are significantly better. So I think that it's the too high / too fast problem that makes me "float" for quite some in the level off and sometimes result in a balloon.

Never the less, thanks for your input

[square]

I don't have a formula for you mate but I would suggest that you do not try to use formulae, because they will not teach or enable you to fly an airplane. The change in winds, density altitude and arrival patterns will all change how you should be flying the airplane. But it's nevertheless quite simple -- your job is energy management. If you have a strong headwind on final, you will need more power to stay on the slope, and no one here can tell you what power setting to use tomorrow. What you need to get used to is keeping your situational awareness up by looking outside and scanning your instruments to see whether you have too much or too little energy. If you're too high and too fast -- reduce thrust or introduce drag; if you're too low and too slow -- introduce lots of thrust to get back on your approach profile right away. If you're either low and fast or high and slow -- manouever the airplane back to where you want to be. Fly it. A proper approach profile is 300 ft up per 1 NM back from the TDZ. But there's no cookie cutter way to fly an airplane, make your own assesments and make your own decisions.

[robertsailor1]

I think Square is giving you the best advice, 3 turns of this 4 turns of that is not the way to learn to fly

[nikcht]

. But there's no cookie cutter way to fly an airplane, make your own assesments and make your own decisions.

I totally agree with you square. Each circuit will be slightly different every time. For example, the winds at circuit altitude might change, might have to extend downwind, following an aircraft that is making really wide or really tight circuits etc.
Basically every descision (on when to reduce power, turn base, add flaps or start descending) is essentially at pilot's discretion. As PIC I feel the need to be as efficient as possible with the aircraft (it wouldn't make sense to fly downind at the same speed as final, or dropping full flaps on downwind). I'm just looking for tips or tricks to help me adapt to the constantly changing situations, while still being efficient. Like dieselbro suggested visualizing "window" that I have to fly through, I find that helpfull since it will give me the same sight picture every time, and set me up for consitent on profile approaches, hopefully resulting in consitent smooth landings. But I realize that getting to that "window" will be different each time.

I guess that's the beauty of flying. No two flights will be the same.

[trey kule]

I just had a very intersting experience two weeks ago that I think is relevant . first of all, many years ago in the US they got into this formula flying, and unfortunately it has creeped into Canada. Here is my latest adventure.

I was doing a check on an new FO. Pretty sharp young man during the oral part, and he had done very well on his technical writtens.

We are doing the first part where you simply take the plane and do a circuit, then get onto the next phase.

The climbout went fine, but when he turned onto downwind he simply was not holding his airspeed. I asked him to confirm his target speed. He did. We were not on it., Then he never did nail the speeds for the rest of the circuit. So what was the problem?
He had got it into his brain that he had to use a particular torque setting for this speed. And he was trying his damnest to do it. At the briefing afterwards ( he did very well on the rest of the flight)When asked what was important, his speed or his power setting at that phase, he said, correctly speed. When I suggested then that if he wanted to maintain a certain speed in level flight he had to understand that the torque may just not be what the book said.
He got it. I did a line check with him a few days ago and it was like I was flying with a new pilot . Target speeds nailed.
so after that flight we did a little training analysis.
Anyone that tells you that this or that combination works everytime and you just add this or that trim really does not understand what they are supposed to be doing, and the advice square and others gave you you should follow. YOU DO WHAT IS NECESSARY TO MAKE THE AIRCRAFT FLY THE PATH YOU WANT IT TO.

As an aside, many years ago we were taught power for altiude, pitch for speed. Now that is technically not correct and was subsequently changed to the correct power plus attitude equals performance. BUT...and here is a big but. Nail the speed. Use power to give you the proper rate of ascent/descent, and then adjust the speed by pitch and a little change in power. It should give you a nice smooth approach without huge adjustments in power and attitude. If you find yourself jockeying with the power and going up and down on the approach you probably have not quite got the appoach picture correct in your brain, but that is another topic, though it was alluded to by CAT. I will leave the roundoff flair and actual touchdown to others as you did not ask about that.
You were very correct however , in your understanding that things change. Wind, density altitude, aircraft weight, position of the C of g in the envelope all will make a bit of difference in how you do things.

enjoy. you have the right attitude, and with practice I think you will get it down just fine.

[gaamin]

nikcht, have you ever tried flying circuits with the whole instrument panel hidden? No distractions, just looking outside and feeling / listening to your aircraft.

With your instructor ensuring you don't bust your altitude too much on downwind, monitoring oil gauges, and correcting things to the right picture, that might help a lot.

[AJV]

Ok, so here is the thing, if you are consistently high on short final then change 1 thing and do it the same for at least 3 circuits, ie if you are going to 1500 rpm then go to 1400. Keep it simple.
I agree with another poster about the flaps on downwind not being required.

Here is a break down of how I teach it

1 2200rpm on downwind get all your cockpit checks done as soon as possible so you can focus on flying the A/C
2 45 degree angle drawn (imaginary) out of the tdz reduce power to 15-1600 rpm (with instructor on board)
3 hold circuit altitude and lower 10 degree of flaps, 80 mph (70 kts) turn base trimming for 80
4 on base lower another 10 of flap for a total of 20 degrees allowing the A/C to slow to 70-75 mph
5 if needed adjust power for high (reduce) low (add) approach but just a little ie 100 rpm
6 50 ft above threshold we have made the runway reduce power smoothly to idle keeping the now slightly down to maintain 70-75
7 as the landing environment begins to rush at you or speed up then transition to the flare
ie cruise attitude and as speed bleeds off then smoothly to the landing attitude.


now going back to number 5
if you were high or low then we would adjust one thing on the next circuit and I usually teach that as being power. Speeds should stay the same as well as turn points unless the winds are messing with you.

what you are trying to achieve is a stabilized approach, as few changes as possible and doing it all the same every time.

hope this helps

[CpnCrunch]

Why so fast on downwind? Isn't 70 or 80kts more normal?

[x-wind]

I really enjoy reading these forums. I was learning how to fly when I first signed on as a member to avcanada, about seven years ago now. What a great resource, people helping other people freely for know other reason then empathy.

Just chiming in that it maybe inadvisable to be slipping with flaps in your 172S. I haven't flown a 172 for a few years but I do recall reading in the POH that it was an inadvisable manoeuvre.

Also, I had a memorable experience in a 182 whistle in a slipping turn with flaps. The airflow over the horizontal stabilizer was disrupted and it resulted in a concerning loss of pitch control for a second or two.

Cheers

[AJV]

recall reading in the POH that it was an inadvisable manoeuvre.

I believe it says with full flaps it is not recommended but it is not prohibited

[Beefitarian]

recall reading in the POH that it was an inadvisable manoeuvre.

I believe it says with full flaps it is not recommended but it is not prohibited

In the cross wind advice it says they can cause an elevator oscillation at settings greater than 20 degrees. I've heard some say they also reduce the effectiveness of the rudder.

[trey kule]

1 2200rpm on downwind get all your cockpit checks done as soon as possible so you can focus on flying the A/C

I am gobsmacked when I read this type of advice. You are not flying a 737 here. Your priority is to nail a speed in level flight in the downwind..You set whatever power needed to do that. to specify a specific power setting is simply ludicrous in a small aircraft.
You can suggest that around that setting should get you the proper speed, but to state as certain RPM...I feel for your students understanding of power/speed relationships.
One of the really bad things to come out of the FTU college graduates is for the inexperienced not to understand that there is a world of difference between a 1600 pound piston trainer and a 100k plus jet when it comes to power/speed settings. the problem is it seems now to be appearing in flight training as these graudates become instructors and want to teach how to set speed on a heavy jet.
I am going to repeat myself..On the downwind, you want a particular SPEED in level flight.....use whatever power is necessary..Do not assume a particular power setting will work, because in a light aircraft it seldom, if ever will.

Am I so out of touch with light plane flight characteristics and modern instructing techniques that this is now considered to be the proper way to fly a plane VFR in the circuit?

[AJV]

1 2200rpm on downwind get all your cockpit checks done as soon as possible so you can focus on flying the A/C

I am gobsmacked when I read this type of advice. You are not flying a 737 here. Your priority is to nail a speed in level flight in the downwind..You set whatever power needed to do that. to specify a specific power setting is simply ludicrous in a small aircraft.
You can suggest that around that setting should get you the proper speed, but to state as certain RPM...I feel for your students understanding of power/speed relationships.
One of the really bad things to come out of the FTU college graduates is for the inexperienced not to understand that there is a world of difference between a 1600 pound piston trainer and a 100k plus jet when it comes to power/speed settings. the problem is it seems now to be appearing in flight training as these graudates become instructors and want to teach how to set speed on a heavy jet.
I am going to repeat myself..On the downwind, you want a particular SPEED in level flight.....use whatever power is necessary..Do not assume a particular power setting will work, because in a light aircraft it seldom, if ever will.

Am I so out of touch with light plane flight characteristics and modern instructing techniques that this is now considered to be the proper way to fly a plane VFR in the circuit?

whoa!! just a second here!! he said he has 10 hours ok? and I merely stated what works in a 172. Now you say fly a speed well that sounds more like 737 to me. think about it you want a fresh guy with his head stuck in the cockpit trying to nail a speed while very green on solo??? or set the power, fly the plane, do it all the same. Once he is proficient at flying the A/C and doesn't go all over the place cuz he is fixating on an instrument then you can say hey 2200 is giving us 82 knots and we want 90 so lets fine tune it.
my 2 cent
Oh and BTW at 10 hours your priority is to fly the A/C safely and that means look outside.....

[trey kule]

Well, as this has become a discussion on flying the speed in the circuit...how about this...You have no business as an instructor in bringing your 10 hour student into doing circuits until they can manage a speed within limits, and do it without being so focused that they fail to look outside the cockpit or lose situational awareness. That should all have been done in the upper air work before you ever started doing circuits. The circuit is not the place to be teaching (or learning) proper speed control. and if the student is not able to control their speed properly, there are going to be other problems in the profile and landing.

But you stated positively to set a specific RPM. No mention whatsoever of speed control. So it would be perfectly acceptable for your 10 hours student to comply with this without any undersanding of the possible differences in weight, c of g location, temperature or density altitude. Just set this RPM....and then exactly how are they to nail the speed? You eyes out of the cockpit..Of course. That is just a red herring .
The fact is you stated a specific power setting . Not a speed and a suggested power to get close to it with minor adjustments, which BTW, a student should have learned to do in their upper airwork without ever looking in the cockpiit except a brief glance once the airspeed has stabalized. The fact is a student must learn to glance at the airspeed, altimeter, engine guages etc. briefly and with an understanding. If they are spending to much time with their heads down doing this, they were brought into do circuits to early before they had a chance to learn proper control of the airplane.

And the good news is if I am wrong, no one will suffer as I do not instruct. The bad news is if you are wrong, your students are going to suffer. Just saying.