Landing the C-172
Problem
Hello,
I'm a 10.6 Hr student and at the moment working on landing C-172s properly. Had a question on the use of flaps when landing. On landing approach, when should flaps be deployed at 10degs, 20degs and full flaps? Why?
Wasn't very convinced with my CFI's response and couldn't find useful pointers in my Jep book. thanks in advance,
praveen
Solutions
Here's what I've found works...
On downwind adjust throttle to give you about 90 KIAS, and get the trim set for hands-off level flight. This will probably be somewhere around 2200 RPM. Remember to add carb heat as you go below the green arc. As you pass abeam your touchdown point, reduce throttle about 100 RPM, put in 10 flaps, and begin a shallow descent. This should give you about 75 KIAS.
After you turn base, reduce power another 100 RPM and go to 20 flaps. This should give you about 70 KIAS. On final, reduce power as required to maintain 65 KIAS. Add in the last flaps on short final when landing is assured.
Roy Smith
#2
As with all things related to aviation, "it depends."
Generally, in a 172, on a day with not much wind or turbulence, 10 degrees abeam the numbers on downwind, 20-degrees when you turn base, and 40 degrees on final.
Why?
To decrease your airspeed and increase your angle of descent. You want to decrease your airspeed to decrease your rollout. You want to increase your angle of descent for obstacle clearance.
Brien Meehan
#3
You have received excellent answers, but let me chime in with this: Don't look to your Jepp book for information on 172s...look in a 172 book. My 172Q book says "As desired (0-10 below 110 KIAS, 10-30 below 85 KIAS) Airspeed 60-70 KIAS (flaps down)"
That's all you have to work with...Jepp can't add anything that the manufacturer has not included in the manual. As Roy says, it is a matter of judgment, and a large part of flight training is developing judgment on what to do, when to do it, and how much.
Bob Gardner
#4
10 degrees abeam landing point on downwind. 20 on base. Full flaps on final. That's how I do it.
John Y.
#5
Can't argue with that, but the official word is to follow the manufacturer's recommendations...when they are vague or open to interpretation, you're on your own. No one can say that what you are doing is right or wrong as long as you stay within the limits set by the manufacturer.
Bob Gardner
#6
That is why the first notch here, the second notch here, and the third notch here, right? I assume you know the steeper angle, better visibility, lower speed at touchdown, greater drag so shorter rollout, etc, as to why flaps are used. If not, other's answered that one. If I'm right in your question, other's will have better answers to it, too, I'm sure.
My belief (I haven't asked, and am a student pilot as you are) is, primarily, to bring the flaps in gradually over the final part of the pattern so there is no abrupt change in attitude. I was taught to lower RPM abeam the touchdown point, hold altitude until airspeed drops, first notch when below Vfe, second on base, third on final. A secondary reason for those chosen three points of bringing in each notch (again, my belief) is as a memory mnemonic. Of course, you have to be careful if it becomes a hard and fast mnemonic.
I have landed where (per the tower) there was no downwind leg or even base leg, where I was directed (by the tower) to do a straight in approach. I didn't have any problem with it, but I remember the straight in was the strangest for me to judge when to reduce power, when to bring in the flaps, etc. On my long solo cross-country, at a towered airport, I was given the option to do a straight in or call left base; I called base to help keep the perspective as close to normal as possible. In either case, I just reduced RPM and brought in flaps as it seemed appropriate. Worked okay. Good luck,
Ricky
#7Y'all,
A couple of opinions that that have been mentioned as possibilities. I like to get as many constants set as soon as possible. I approach the numbers at cruise on downwind. At this point I reduce the power to 1700 rpm in anticipation that the deceleration will reduce rpm to 1500. The speed of Cessnas at this point allow the appropriate pattern size to be established with three full moves of the nose up trim wheel. The speed while holding heading and altitude will be at 90 knots hands-off. Put in 10 degrees of flap and take off one turn of trim. Speed will be hands-off at 80 knots.
Turn base in 30-degree bank, put flaps to 20 degrees and take off one more turn of trim. Speed will be hands-off at 70 knots. Turn final and put flaps to full and do not change trim. Speed will decrease to 60 knots hands-off and no-flap go-around trim without any change speed is 75 knots. Aircraft loading will make small differences in these speeds but trim settings are pretty constant.
Did six x-wind landings in 90 degree/30 knot winds this morning. Used no flaps and final approach speed of 70 knots in order to hold runway and nose alignment. Floated 1500 feet from threshold to touchdown with one go-around due to poor runway alignment. Definite decrease in wind velocity below 20 feet. Pretty near maximum capability for me. Uncontrolled airport with no traffic.
Gene Whitt
#8
Use as per the POH as other have suggested (probably 10 on downwind, 10 more on base and the rest on final). But understand this: The flaps are there to provide extra lift. When you have extra lift, stall speed is decreased by probably around 3 knots per flap setting in your plane (you need to know this exact figure so study your POH). When you have less speed upon landing, energy decreases significantly.
For example, you are about five percent fast on final approach. That 5% extra speed (just 4 knots or so) adds TWENTY PERCENT to your landing distance. Not good on a short field. It's for this same reason that you want to be going as slow as possible when the wheels hit the ground during a landing. In the event of an accident, you don't want any extra energy. About the only time you don't want all the flaps on final is in gusty conditions.--
Jim Fisher
Y'all,
In my experience with teaching landings, problems arise when basic skills are not well seated. I will review slow flight in all configurations, ground reference maneuvers, the four basics and stalls. I do these while en route to nearby airports not previously visited. We will do landings with taxi back or stop and go and perhaps make departures with return from various checkpoints to practice radio procedures. I want to do as many left patterns as right patterns when conditions allow as well as short runways.
Gene Whitt
Traffic Pattern
Problem
Today was the second close call I've had this week. On Monday, someone without clearance, somehow cut in front of me while I was on short final. Today was a busy day at the airport, a lot of commercial traffic. Me and a 172 were doing touch and goes. He was put on right traffic and I was told to do the same. When I turned on downwind, I didn't see him. (Tell the tower when you can't see traffic. Ask them to call your base. ) We were both told to extend downwind. Still no contact. While looking for the 172, I let my heading stray. He turned base and I still couldn't see him. All of a sudden he appeared maybe 1000 feet ahead of me and was turning right toward me. After saying a few choice words to myself, I turned base. When I looked to the right for the runway. It wasn't there. I turned to what I thought was final. Turned out I let the heading drift so much that I was on what was
usually a left base. My head wasn't on right or something.
I'm really starting to rethink my flying career at this point. I try to be a safe pilot but my performance lately really debates that. I just don't know. (You are not alone. In the interval from when you were spending considerable time in the pattern with the instructor and when you began going places, you lost some of your skills. The best part of what happened is your realization that you needed some ideas.) Any criticism or motivation you can offer?
Gene's Advice
When complex situations such as pattern flying begin to give you trouble, I like to suggest going back and review the basics. In this case, pattern flying related to ground reference.
First, at altitude, practice making some 90-degree turns at 80, 70 and 60 knots. Do the turns while level, climbing and descending in both left and right turns. Time them so you get some idea of how long it takes to make a 90-degree turn banked 30-degrees. Make all pattern banks at 30-degrees and never steeper. By making a constant bank in the pattern and leveling off 15-degrees early you will develop a consistency that will help keep things close to 90-degrees without timing. I tried a little poem during the turn and found that reciting it would give me 90-degrees every time at 30-degrees of bank. Remember the time will change, for each airspeed, but not by much.
I know that you usually do ground reference watching ground references. What I am suggesting is that you do your ground reference using the directions at your home airport. Since you seem to have a tower do the patterns both left and right but referencing your heading indicator for upwind, crosswind, downwind, base and final. Make your turns all with a 30-degree bank. Do the patterns at pattern altitude and change airspeeds just as you would in landing but maintain pattern altitude.
As you fly the patterns you will note that any wind will affect just how rectangular the pattern will be. Once you determine the effect of the wind on your track over the ground you want to go back to where you first started and fly the patterns with an estimate of the wind correction required on any one of the four legs. suggest you do this for at least a half hour but maybe longer until you can fly the patterns using both the heading indicator and the ground references.
Last, add flaps, descents and go-arounds to your pattern but keep a good watch for traffic. Never make a turn without clearing before the turn. Be trimmed so you can let go of the yoke on every straight leg. Remember to lead with right rudder every time you add power or raise the nose.
You won't have a pattern traffic problem if you can increase your traffic watch and decrease the time you need to fly the aircraft. Do what you can to improve your flying skills in the pattern and you will have more time to watch for traffic.
More if you wish...
Gene
Continue To Next Page