We’ve all been trained to deploy full flaps when executing normal landings and flying airplanes that have them. The reason is fairly simple: the full-flap setting provides the most lift at low speeds, which is desirable when landing. “Normal” is doing a lot of work here, since what might be a normal landing to you and me might not be to someone else. The good news is there’s no rule that says we have to use full flaps when landing a typical personal airplane.
That’s not the same as saying we shouldn’t use full flaps when landing. In fact, the FAA long ago took a self-inflicted hit when it decreed a “normal landing” was one in which full flaps were deployed. The problem is that no one really agrees on what a normal landing looks like. Is it one lacking a crosswind component? Is it one made to a paved runway with some specified length or width? The punch line is that each landing is different, and while full flaps probably are recommended for your airplane, it’s up to you to decide whether they’re appropriate. What are some of the reasons you might not want to use full flaps when landing?
Gusty Crosswinds
The poster child for not using full flaps probably is the gusty crosswind, and it may have a lot to do with the very effective Fowler flaps installed on many high-wing Cessna singles. The things are huge, and when fully deployed to the 40-degree setting many legacy Cessnas feature, create a lot of drag along with lift. In a gusty crosswind, however, they can be a liability if the pilot uses poor technique and lets air get underneath the upwind wing, lifting it and altering the airplane’s trajectory at the wrong moment. As a result, savvy instructors working in crosswinds with low-time students often suggest using some intermediate setting to minimize the possibility of losing control if/when a gust tries to lift the wing.
Other airplanes may not exhibit the same characteristics in a crosswind. They’re likely a low-wing design, placing the wing closer to the surface and making the gusty crosswind’s attempt to raise it and spoil the landing more difficult. They also may not feature as much maximum deflection as the legacy Cessnas. In fact, the last legacy Cessna 172, the 172P, and the 1996 and later 172R and S models are limited to a maximum of 30 degrees of flaps.
Purists will complain that they’d still like the option of the full 40 degrees, but Cessna’s decision to limit flap travel highlights that we don’t always have to use full flaps. Regardless of the airplane and its configuration, using partial flaps when landing in a gusty crosswind has benefits. They include reducing any gust’s tendency to lift a wing and help us carry a few extra knots—no more than the recommended half the gust value, please—into the flare to help improve control authority.
Keep Your Speed Up?
Using partial flaps—we’re leaving no-flap landings out of this discussion—can come in handy in situations other than crosswinds. If you’re flying a twin on one engine, it’s probably not a good idea to even think about using full flaps on landing if there’s any chance you’ll have to go around, however unlikely a successful attempt may be. Diamond Aircraft’s airplane flying manual for its DA62 twin, excerpts from which are reproduced below, suggest lowering full flaps only when reaching the runway is assured.
Of course, the need to go around can arise in any airplane. Unless they’re relatively ineffective, climb rate likely will take a major hit when full flaps are deployed and you’re trying to climb. If a go-around is likely, applying only partial flaps—at least until a landing is assured—is preferred.
Getting the flaps headed to the retracted position can be as simple as repositioning a switch, but you may not have control over how fast it happens. Quickly reducing a flap setting, especially full flaps, will result in at least a momentary loss of lift every time. You’re the judge on when and how fast retraction is appropriate, and on how much cockpit workload is too much, so it’s important to remember that a partial flap setting typically affords better go-around performance and minimizes distractions.
A key here is knowing what conditions you face for your landing and properly configuring the airplane ahead of time. Using flaps minimizes groundspeed at touchdown, and slower is better, minimizing wear and tear on the airplane. That’s the main reason full flaps are considered part of a “normal landing.”
Getting To Know Your Flap Settings
Even if you’re a student who’s just learning to land, you have some idea of how effective your airplane’s full-flap setting is. But you may not have spent much time flying it with partial flaps. There’s an easy, fun fix for that: go fly. At altitude, slow the airplane as you would for landing, but add only partial flaps, and then let the airplane approach a stall as you would if the runway were a few feet beneath you. Then add full power and establish a climb. Note the climb rate at the partial flap setting and recommended airspeed, and then recover, noting the time it takes to fully retract the flaps.
Do it again with full flaps. This time, pay particular attention to flap retraction time and how the airplane reacts to the sudden loss of lift. Try retracting the fully extended flaps more slowly next time. Repeat as necessary to ensure you can both handle the configuration changes and obtain the kind of performance you need.
The idea is to find a sweet spot as you juggle airspeed, pitch trim and rudder input while losing both lift and drag. Once you have an idea of the appropriate settings, apply them for some calm-wind go-arounds, and then graduate to gusty crosswinds. Knowing how the airplane responds to different flap settings can pay big dividends when you’re doing it for keeps.
This article originally appeared in the November 2021 issue of Aviation Safety magazine.
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The article doesn’t mention slips with flaps. And I’m hesitant to mention it because I have spent a lot of years trying to correct the myth that “Slips are ‘prohibited’ with flaps extended” in Cessnas.
(They aren’t prohibited. The placard said “Avoid.” And while we’re at it, there’s no such thing as a Ramp Check for Part 91 pilots either.)
But since one can perform a slip with flaps extended, one should know how their aircraft behaves if different.
It used to be that C-172’s had a placard that said “Avoid slips with flaps extended.” (I don’t recall seeing it in 150’s, 152’s, 182’s, Gutlesses or 210’s.)
Now that I’m renting lowly (but newer) C-172’s again, I don’t see the placard anymore.
I confess that I haven’t searched through the Pilot’s Operating Handbook to see if there’s still something said about it.
But I correct my sin and just now I reviewed the latest Handbook. (Isn’t the Internet fantastic?) It now says in the Handbook “Steep slips should be avoided with flap settings greater than 20 degrees due to a slight tendency for the elevator to oscillate under certain combinations of airspeed, side slip angle, and center of gravity loadings.”
(Which is kind of interesting. It says “side slip.” Like the airplane knows where the wind is coming from and knows the difference between a side slip and a forward slip?)
In approximately 2000 hours of flying the 172 variant, this happened to me only once. And I was never able to reproduce it on subsequent flights. (And I like to slip. A lot.)
As the advisory says, the yoke oscillated – about 3 inches in and out – at about 1 cycle/second – while in the slip. Strangely, the attitude of the aircraft did not change with these uncommanded changes in elevator position. It was almost like an Autopilot went loco – although there was that “pseudo-disconnect” in the elevators. (Somewhat like in a stall – but there was still pressure in the yoke.) I remember thinking “Ahh! THIS is what they are talking about.”
My guess is that one side of the elevator could get into fuselage wake during the slip. (Maybe after Cessna changed from the straight tail 172’s?)
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It turns out that when I used to work for Cessna’s Radio Division, I had heard a story of how this placard came to be. One of our Cessna pilots in my Division knew the 172 test pilot in Wichita. Apparently that test pilot had tripped across this strange oscillating behavior too. (Which is rather amazing that he found it, considering that it has happened to me only once in my lifetime.) The test pilot was concerned about it, and wouldn’t sign off the plane unless Cessna made a placard about it.
Now that I’m older, I would like to have known more of the backstory. Did the test pilot not want to certify the airplane for slips with flaps at all? How does one avoid doing this, since a crosswind landing involves a slip? THAT would have been a deal breaker. (Like using “too much” rudder in an Airbus?)
Very interesting comment – thank you. I haven’t found the oscillation to be so much – more like a half inch forward and back of the control wheel. As the POH says, there’s no loss of control. I discuss that quote in the POH with students and demonstrate it before solo so there’s a complete understanding, and no fear in using a slip with full flaps if it becomes necessary for some reason. But this is not the case with all models out there. A pilot who flies a C170 once commented that he had lost I think two friends when doing a slip with flaps on final and pitch authority was lost. I was able to find a POH and the warning is clearly stated – “Slips with full flaps are to be avoided because if the slip is extreme enough at a relatively high airspeed, the airflow is disrupted over the tail surface resulting in a sudden and steep, downward pitch of the nose”.
All you have to do is take out the slip if you actually experience the sudden nose drop and the plane will fly normally again. I have slipped all kinds of various single engine Cessnas including a Caravan and yes I have been able to get to oscillation in pitch slipping a C172 but all I had to was release the control pressures holding the slip and the plane almost instantly returned to normal flight characteristics on the approach.
Ummm…not sure about your statement “And while we’re at it, there’s no such thing as a Ramp Check for Part 91 pilots either.” As someone who has conducted a number of them “Yes Virginia, there really are 91 ramp checks” and here is a link to the who, what, when, where and how to do them: https://fsims.faa.gov/PICDetail.aspx?docId=8900.1,Vol.6,Ch1,Sec4
Thanks.
As it goes to Part 91 PRIVATE pilots/operators (in contrast to Part 135, 141 COMMERCIAL ops, who hold out to the public and so waived certain constitutional rights to do so), the “Order” that you linked says, “An inspector MUST NOT open or board any aircraft without the knowledge and consent of the crew or owner/operator.” (See 6-89(B)(1). Emphasis mine.)
[For those following along, you have to scroll in the window that presents in the link that Max supplied to read the rest of the text. Or try this link for the whole html.
https://fsims.faa.gov/wdocs/8900.1/v06%20surveillance/chapter%2001/06_001_004.htm ]
So, fortunately, even the FAA acknowledges here that Private Pilots have a 4th Amdt right as it goes “Ramp Checks.” (Although the FAA violates our 4th Amdt right when it “conducts routine surveillance activities” ((C)(4)). The 4th Cir recently ruled that such unwarranted surveillance is unconstitutional.) Specifically, we do NOT have to let the FAA into our airplane/cockpit, etc. In fact, as with cops, we don’t even have to talk to the FAA.
The most that we have to do if the FAA asks is to “present” (i.e., show – not surrender, which was Bob Hoover’s mistake) our certificate and medical. (And, now, photo id.) And the FAA can peer through a window to see that an Airworthiness Certificate is “legible.”
I don’t doubt that you conducted Ramp Checks on Part 91 Ops. And I don’t doubt that almost everyone waived their 4th Amdt Right and let you do it.
But to conclude that there are Ramp Checks for private pilots because you did it is like a cop saying that it’s okay to enter someone’s home without a warrant because he did it all the time.
Agree that the generalization of “normal landing” is inappropriate. But the rest of the article… speculation, ignorance, and out of context generalizations.
Way too many errors to comment on them all.
Whoa….
Chill, be nice or be quiet
Use of flaps depends on the type of aircraft and the type of flying. When making a “normal” landing in a Cessna I teach partial flaps is normal, i.e. use 20º normally and save 30º or 40º for short-field operations. Conversely, for a Cherokee, Mooney, CAP10B, Grumman, Bonanza, Yak52, CJ6A, I teach the use full flaps on all landings … unless I am doing a no-flap landing. Hmm, I am detecting a pattern here.
And then there are different flap types: split flap, simple flap, slotted flap, Fowler flap. That changes how one uses flaps too.
Bottom line: I don’t think it is prudent to generalize on flap usage for aircraft B based on flap usage for aircraft A. Start with the PoH. Use that as your baseline. After you do that, go practice (as suggested in the article) and determine aircraft (and pilot) behavior for yourself. Once relatively familiar with aircraft behavior at altitude, try it in the pattern.
There are too many different airplanes out there for this article. No flaps, partial flaps, full flaps… the only right answer is “it depends.” You could have written the piece on the 172 or other popular aircraft and it might have been more useful.
My standard of comparison is between my old C-182 with its 40-degree range (quasi)Fowlers and the wimpy boards on my somewhat newer A-36 Bonanza. With the Cessna you actually have a lot to play with, a spread of choices between lift and drag with something to fit every scenario. Now, I like the Bonanza fine, but in terms of flap usefulness, meh.
The C-182, BTW, can also exhibit elevator oscillation in a hard full-flap slip.
And then, the many vintage aircraft with no flaps. Me having flown them so much, I tend to make most of my Cessna , etc landing no flaps. I’m of the “use flaps if you need them” thought…kinda, but not for every landing. As others said, actually an aircraft specific debate.
The biggest benefit for partial or no flaps in a crosswind to me is easily the improved rudder authority. With full flaps, especially in a 40° Cessna model, the rudder feels quite mushy. Go to 20° or less, and the rudder authority is far better.
This reminds me of something I observed during an end-of-lease return on an EMB120 in the ’90s. The US-based airline had been looking for ways to save $$ and had analyzed the flight performance of the EMB120 and found that using partial flaps and power set to maintain G/S consumed a significant amount less fuel than using full landing flap. This is somewhat obvious but they quantified it. Over time, the savings would build up such that they adopted the practice fleet wide. Fuel cost savings way outpaced the slightly increased tire & brake wear. They also coincidentally found that doing so increased the mean time between removal (MTBUR) of the flap power unit (which was a notorious weak point) because it didn’t experience the high aerodynamic loads of landing flap configuration further lowering their operating costs. Just some food for thought.
Not an inaccurate thought on their part. I once rented from an FBO, C172, who said do not use flaps unless you need 10 degrees for a soft field takeoff, which you shouldn’t be doing in my airplanes, or full flaps if needed for steep descent on rare occasions. Otherwise, you are just wearing out the flap motor and the flap tracks unnecessarily.
Once you get into transport category planes you may not have a choice but to use full flaps for landing. When I was training in the sim for my C500 type, we were told to always use full flaps for landing because the local FAA rep considered partial flap landings in the Citation 500 series an emergency action. So even then it can depend on what FAA persons interpretation is.
Just a note of interest relative to flap settings, but I flew a Maule M7 on floats at Jack Browns’, and it was the only airplane that I have flown with a NEGATIVE flap setting, and my instructor made sure I was aware of that.
As a GA CFI, I recommended landing practices, using none, as little, or as much flaps as needed-depending on winds, aircraft, and fuel level in tanks as in some aircraft fuel may shift away from intake ports on prolonged slips causing fuel starvation. Read manual.
Also, I explained and included landing practices with no flaps in case any of the electric flap system components (relays, motors, switches) fail to activate them. Some Cirrus pilots never or seldom do this, and when components fail, they find themselves wondering, landing faster and using more runway to a full-stop than expected. I learned this one by experience.
It has been my experience that in the Cessna 100 series and similar designs, full rudder slips with full flaps may disrupt airflow to the horizontal stabilizer causing a significant tail downforce reduction (lift) allowing for the tail to suddenly come up, and the nose to go down. I have tried several full flap, full rudder simulated approaches to a landing, out of 4000 ft, in a C172H, and encountered this tail up stall effect with a 400 ft loss on recovery. The control vibrations will tell you to let go of the slip, level wings, apply power, and go around if so.