C172 slips with flaps...POH's updated?

Discussion in 'Flight Following' started by scooter, Aug 27, 2015.

  1. scooter

    scooter Pre-Flight

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    I've read that there was a change to the C172 manuals removing the "avoid slips with flaps", and in earlier planes "slips with flaps prohibited".

    Was discussing with a CFI and want to find a reference that documents the removal of the wording from the manuals.

    Any one have any ideas where to find a reference?
     
  2. ksandrew

    ksandrew Pre-Flight

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    Scooter,

    Are we allowed to change the POH?????? I have a situation where I am instructed to take off on left tank or right, not both. before Ser# xxx, My plane has been modified with the newer fuel selector where the POH says take off on both tanks.

    Common sense tells me to use both tanks, but we are dealing with the FAA.

    Life is a barrel of fun.

    Ken
     
  3. txflyer

    txflyer En-Route

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    I don't care what the FAA or the POH says, I'm not slipping mine with 40* out I can tell you that.

    Sorry I can't be more helpful to your specific question ...
     
  4. German guy

    German guy Cleared for Takeoff

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    May I ask why not?
     
  5. nosehair

    nosehair Cleared for Takeoff

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    Because he doesn't want.
     
  6. Clark1961

    Clark1961 Touchdown! Greaser!

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    Exactly.

    Try it at a safe altitude...
     
  7. txflyer

    txflyer En-Route

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    Tail stall.


    [​IMG]
     
  8. Clark1961

    Clark1961 Touchdown! Greaser!

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    reality trumps imagination every time
     
  9. Jimmy cooper

    Jimmy cooper En-Route

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    Flying a cessna 180 there is no need to slip it. . The flaps on a 180 are very effective and make a slip unnecessary. When you yank on full flaps in a 180 you quickly see a slip is totally unnecessary. Slips were used in older aircraft like Taylorcrafts, Cubs, champs, etc. As they did not gave flaps. A 172 is a very docile aircraft and if your used to it you should not need to slip it but if you must, do it.
     
  10. MauleSkinner

    MauleSkinner Final Approach

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    Ask Cessna for a current list of effective pages for the manual.
     
  11. mkosmo

    mkosmo Pattern Altitude

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    What makes you think you'll tail stall? I don't know about the 180 (so what I'm about to say may be irrelevant), but at least in the 172, you get some benign washout that feels funny but doesn't cause any danger. It's a neat oscillation in the elevator feedback, but it's harmless.

    I'll tell you I can drop quicker than a washing machine that way, too!
     
  12. woodchucker

    woodchucker Pattern Altitude

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    I'm a bit confused. Why are they asking for full flaps slip-to-land during check-rides in 172s then?
     
  13. txflyer

    txflyer En-Route

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    I have no idea what you mean. :confused:



    I agree 100% :)




    Because I've tried it and it got weird, and more than one old skywagon pilot has warned me not to do it. Good 'nuff for me.... :dunno:
     
  14. mkosmo

    mkosmo Pattern Altitude

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    I'd give it a shot if I were you, then. There's a lot of folk-lore misinformation in aviation... some of the incorrect rumblings really need to get killed off, too.

    If you just get mild pulsations in the yoke, it's exactly what I'm talking about. It took a very specific degree of slip and it didn't even always wash out the same, but it sure didn't feel like a tail stall!
     
  15. txflyer

    txflyer En-Route

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    I'll dig out my POH when I go to the field, I think it's in there not to do it with full flaps.

    There's quite a bit of difference between 30* and 40* flaps. You may get away with it in a 172. They don't have 40*. Very short final with a low AGL is the last place I want to feel pulsations in the elevator.

    It's superfluous as it was said because with 40* out and chop the power mine will drop like a stone so I never need slips. They're fun, but the times I've done it in mine it feels like too much stress on everything. Skywagon's have a lot of rudder authority. It feels like it's stressing the airframe beyond what I'm comfortable with.... :wink2:
     
  16. mkosmo

    mkosmo Pattern Altitude

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    I have 40 degrees of flaps in my 172! I'd miss not having them if I had a newer one.

    Sent from my SAMSUNG-SGH-I337 using Tapatalk
     
  17. txflyer

    txflyer En-Route

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    I did not know that ... learn something new every day.

    What year did they stop?
     
  18. mkosmo

    mkosmo Pattern Altitude

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    They had them through the N model. In 80 or 81 when the P came out, they changed maximum deflection to 30 to get a MGW increase. Earlier models get a +250lbs MGW STC for paperwork and a flap limit of 30.

    Sent from my SAMSUNG-SGH-I337 using Tapatalk
     
  19. mjburian

    mjburian Cleared for Takeoff

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    Have you done this? We have a 172N and thought you needed an upgrade (engine to 180hp or PowerFlo exhaust, etc) in order to get the MGW increase STC. Can we really just pencil whip it and limit flap usage to 30*?
     
  20. mkosmo

    mkosmo Pattern Altitude

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    The STC I'm thinking of doesn't require any engine change, just the flap limit. Unfortunately it's a permanent install... Can't trust us to self limit when taking advantage of the additional weight. I have not done it because I like flaps 40!
     
  21. flyingron

    flyingron Touchdown! Greaser! PoA Supporter

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    The 172 slips with flaps is not a tail stall. It's turbulence from the air coming off the flaps.
     
  22. Pilawt

    Pilawt Final Approach

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    The Air Plains STC SA2196CE, which limits flaps to 30 degrees, increases gross weight on the 172N with the original 160 hp engine by 100 pounds, to 2400 pounds. That makes it the functional equivalent of a stock 172P. If the 180 hp engine is installed (STC SA4428SW), then gross weight is increased by 250 lb, to 2550 lb., making it the functional equivalent of a stock 172Q "Cutlass" (fixed gear).

    I have both STCs for my 172N. The 180 hp engine has been installed, but the flap limiter has never been installed. So I still have 40 degrees of flap, but only the original 2300 lb gross weight. Maybe someday I'll install the limiter, but not now. I like short fields and I have no friends. :D

    No. The mechanical limiter has to be installed in the flap linkage. Here's mine:

    [​IMG]
     
    Last edited: Aug 28, 2015
  23. Pilawt

    Pilawt Final Approach

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    Nope, that's not it at all.

    Here’s what Bill Thompson, former Manager of Flight Test & Aerodynamics at Cessna, had to say about the issue of slipping with full flaps in the 172 (Cessna — Wings for The World, by William D. Thompson, Maverick Press, 1991, p. 41):
    With the advent of the large slotted flaps in the C-170, C-180, and C-172 we encountered a nose down pitch in forward slips with the wing flaps deflected. In some cases it was severe enough to lift the pilot against his seat belt if he was slow in checking the motion. For this reason a caution note was placed in most of the owner’s manuals under “Landings” reading “Slips should be avoided with flap settings greater than 30 deg. due to a downward pitch encountered under certain combinations of airspeed, side-slip angle, and center of gravity loadings”. Since wing-low drift correction in crosswind landings is normally performed with a minimum flap setting (for better rudder control) this limitation did not apply to that maneuver. The cause of the pitching motion is the transition of a strong wing downwash over the tail in straight flight to a lessened downwash angle over part of the horizontal tail caused by the influence of a relative “upwash increment” from the upturned aileron in slipping flight. Although not stated in the owner’s manuals, we privately encouraged flight instructors to explore these effects at high altitude, and to pass on the information to their students. This phenomenon was elusive and sometimes hard to duplicate, but it was thought that a pilot should be aware of its existence and know how to counteract it if it occurs close to the ground.
    [emphasis added]
    The larger dorsal fin introduced on the 1972 C-172L apparently eliminated the issue.

    These images illustrate the upwash from the upturned aileron encountering the horizontal stabilizer. In the first image the airplane is in coordinated flight; in the second it is in a slip to the left. In both images the airplane is tracking (in still air) toward the mountain peak in the distance.

    [​IMG]

    [​IMG]

    There is a separate, unrelated phenomenon that Thompson described in newer models in full-flap slips: “a mild pitch ‘pumping’ motion resulting from flap outboard-end vortex impingement on the horizontal tail at some combinations of side-slip angle, power, and airspeed.” This is entirely benign and common with other high-wing airplanes. My Sport Cub did the same thing.

    So although the 172L’s larger dorsal solved the pitch-down issue, they kept the cautionary note in the POH because of the latter phenomenon.

    Unfortunately Cessna contributed to the “end of the world” fear of slips with flaps, by not explaining the phenomenon in the manuals; and in fact, many earlier C-172 manuals expressly said that slips with full flap were prohibited. I rummaged through my collection of old Cessna owners manuals:
    1958 C-172: “prohibited”
    1959 C-175: “prohibited”
    1966 C-172F: “prohibited”
    1972 C-172L (first year of the big dorsal): “should be avoided”​
    The manuals for these older models have been revised since then, and in fact the TCDS no longer carries the prohibition against slips with flaps. The POH for the current C-172S indicates that it's no biggie:
    Steep slips with flap settings greater than 20° can cause a slight tendency for the elevator to oscillate under certain combinations of airspeed, sideslip angle, and center of gravity loadings.
    But a lot of us old-timers read the scary language in the old manuals back then and that's what we remember.
     
    Last edited: Aug 28, 2015
    Walboy likes this.
  24. txflyer

    txflyer En-Route

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    Very informative and good post. :yes:
     
  25. mjburian

    mjburian Cleared for Takeoff

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    Thanks for the info! Having never personally dealt with an STC before, is this something we handle through our maintenance shop or something we buy from Air Plains and then have the mechanic install for us? (I'm sure our maintenance officer would know, I'm just curious.)

    To the OP, sorry for distracting from the original thread purpose so I'll offer my experience:

    I've slipped with flaps before, both in training and during my PPL checkride. Not all that often since. The "avoid" is the key for me. It doesn't say "not approved" or similar, so while I have done them in the past (and may again in the future, if I feel it necessary), I do tend to avoid them.
     
  26. Witmo

    Witmo Pattern Altitude

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    It's called max performing an airplane. You may never need to do it until the day you need to do it. I once flew with a guy who refused to use full flaps or slip, ever--said he never needed more--he was an idiot, AKA a poor pilot. He always landed fast and heaven help him if he ever had a forced landing into a small field.
     
  27. James331

    James331 Ejection Handle Pulled

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    I didn't think any 172 was PROHIBITED from slips with full flaps, also I've never had a issue slipping one with full flaps and did it frequently on the occasions I would fly a 172, also did slips often in 206s and 208s.


    Do you have floats or skis?

    My 185 is marked to AVOID slips while on floats, skis or amphibs, like you said though, with full flaps in a skywagon, especially with the Robertson drooping ailerons and fences, I have yet to get into a situation where I felt the need to kick her into a slip.
     
  28. UngaWunga

    UngaWunga Pattern Altitude

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    On my checkride, he set up up to be way too high on final, said my engine was out and I needed to land. Slips with full flaps were not recommended, so I did some S turns to loose speed and altitude.

    Not that it answers your question...:lol:
     
  29. James331

    James331 Ejection Handle Pulled

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    In that situation I would have slipped to each their own.

    Given enough hours a slip will save your bacon at some point.
     
  30. Jimmy cooper

    Jimmy cooper En-Route

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    I call it trying to have the last word. I know all about slips and flaps having owned a Stearman , a 195 and many light taildraggers. I've also landed twice with engine failure. Grow up.
     
  31. Stewartb

    Stewartb Final Approach

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    My 180 placard says Avoid Slips with Flaps. No limitation, just a suggestion. I think slips w/flaps are prohibited with wheel skis. No matter, like was said earlier, there's no need to slip with full flaps in a Cessna.
     
  32. Witmo

    Witmo Pattern Altitude

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    "...AKA a poor pilot..." Touched a nerve, did I?

    I would encourage every pilot to get with an instructor and do some max performance maneuvering and landings. You never know when it might come in handy and your typical technique to land on a 4000 foot paved runway might not serve you well when the only clear space is 1000 feet long with tall trees all around it.
     
  33. Stewartb

    Stewartb Final Approach

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    1000' surrounded by trees IS a long strip! No slips needed. Not in a Cessna, anyway.

    I've yet to fly a Cessna that I can't get into places shorter than I can get back out if.
     
  34. BiffJ

    BiffJ Pre-takeoff checklist

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    I've got a 1960 175A and there is nothing in the manual concerning flaps and slips. The plane has 40 deg flaps. Having started out in Taylorcrafts and other flapless planes I use slips and in the Cessna I use flaps too. I've done some experimenting with slips and flaps up to 40 deg and other than some light buffeting there have been no issues. The airframe is essentially the same as the 172 of that era so why the placards and warning in the POH for the 172 but not the 175?
    I do recall the warnings from checkouts in 172's early on but with good instructors who explain why the warnings are there its much less of a concern... some demos helped too.

    Frank
     
  35. James331

    James331 Ejection Handle Pulled

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    Depends on the Cessna, that isn't anything out of the norm for a Skywagon, and in doubt I'd NEED to slip her in, especially with the "standard issue" STOL mods most of the fleet has.
     
  36. baboss

    baboss Pre-takeoff checklist

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    Just another data point:

    1967 Model 172 & Skyhawk Owner's Manual (p/n D638-13-RPC-300-4/86) - this model has 40* flaps from the factory

    Section 2: Description & Operating Details​
    LANDING​
    "Normal landings are made power-off with any flap setting. Slips are prohibited in full flap approaches because of a downward pitch encountered under certain combinations of airspeed and sideslip angle."​
     
  37. Pilawt

    Pilawt Final Approach

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    Some manuals said they were (see below). But whether those old owner's manuals carried the force of law is another question.

    Me neither. But when I do I'm aware of the "elusive" pitch-down phenomenon (unlikely in my airplane with the long dorsal) and ready to react if it occurs.
     

    Attached Files:

    Last edited: Aug 28, 2015
  38. mkosmo

    mkosmo Pattern Altitude

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    Exactly how that works. I'd just ask my mechanic to buy and install it, but I believe Air Plains will sell it direct to you. Don't quote me without calling and asking them directly, but I seem to recall reading something on it.

    Exactly as Pilawt said above, prior to 1972 they actually did. In 1972 the wording was changed from prohibited to avoid with the change in the dorsal design.
     
  39. RoscoeT

    RoscoeT Pattern Altitude

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    It seems this silly slips with flaps controversy will outlast the cockroaches.
     
  40. Shepherd

    Shepherd En-Route

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    I do it all the time. It's not like the plane is going to break up into little flaming pieces.
    At a certain spot, going into a slip, the rudder will stall, coming out of the slip it's not much of an issue.

    As long as you are aware of the aerodynamics, and maintain control past the area where the rudder stalls it's a NOP.