Slips with Flaps
POHs 172
The owners manual for the 1967 Cessna 172 states on page 2-11
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.
The 1976 POH requires a placard which states "AVOID SLIPS WITH FLAPS EXTENDED"
Landing section for Normal landings states:
"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, sideslip angle, and center of gravity loadings."
"The maximum allowable crosswind velocity is dependent upon pilot capability rather than airplane limitations. With average pilot technique, direct crosswinds of 15 MPH can be handled with safety." No max demonstrated crosswind speed is in the POH. The 1967 model has 40 degrees of flaps available.
The 1970 (C172K) model's POH (1970 model also had 40° flaps) has been changed to read "Slips should be avoided with flap settings greater than 30° ..." No required placard is noted in the Limitations section.
Placards are required by model:
According to the TCDS 3A12 (covering models 172 - 172S), regarding slips, the following On flap handle,
Models 172 through 172E:
"Avoid slips with flaps down."
Near flap indicator Models 172F (electric flaps) through 17271034, excluding 17270050):
"Avoid slips with flaps extended."
Tom,
The 172 manuals suggest, but do not restrict, not slipping the aircraft with more than 20 degrees of flaps. On that model doing so would occasionally induce "elevator oscillations." No such notation appears in the 182 POH, or the POH of any other model Cessna besides the 172, because no such elevator oscillations have shown up in full flap slips on other models. Probably has something to do with different fuselage lengths and tail sizes. Having intentionally gotten a 172 in this configuration in my flight instructor days, I did after much effort, get some elevator oscillation. No big deal, just some momentary change in stick force at the control wheel. Plane remains fully controllable, however, I can see where it would be disconcerting for the pilot, particularly if it occurred during the landing flare. But again this only applies to the 172.
John Frank, CPA Tech Rep mailto:
[email protected]