Sorry Colin :-) I reckon what I say is correct in any phase of flight where there is positive G on the wing. An exception is if you conduct a pushover. In that case, I agree, you cannot stall at zero G and airspeed can safely drop right off, eg., like in a wingover.
Under any positive G, if you fly close to the stall (whatever it might be) and then induce a side slip you risk the stall and possible spin irrespective of whether you are descending, climbing or maintaining level flight. You must put the stick forward and on descent this will produce an increase in airspeed. I sincerely hope you are not teaching students to conduct sideslip approaches at the same airspeed as that applying to a balanced approach. If so, you are eating into your safety margin in my humble view. Even worse if you have some flap out masking the elevator effectiveness, eg., the Cessna 150 where slips are prohibited under flap. Regards John. ----- Original Message ----- From: "Colin Rainey" <[email protected]> To: <[email protected]> Sent: Thursday, February 09, 2006 1:24 PM Subject: KR> slipping and stalls > John > All of that would be true in level coordinated flight. > But in a slipping descent as in ANY maneuver while DESCENDING, IF a pilot > does NOT > attempt to remain level, but rather continues the descent, than the > maneuver > does NOT > increase the load factor on the wings. Load factor is what increases the > stall speed. > The descent has already reduced the angle of attack. This is why you are > descending > in the first place; lack of enough lift to remain in level flight. > What killed those pilots you spoke of is the classic crossed controlled > stall, usually > on the base to final turn, but could happen at any point, where the > airspeed > appears > to be high enough, due to what Larry pointed out, a misalignment to the > relative > wind, as compared to normal flight. The exposing of the fuselage side to > the > relative > wind causes an increase in drag, which if the nose is not lowered to > counter, can > cause a TREMENDOUS loss of airspeed quickly. A Tiger Moth has the added > problem > of being a biplane, already with a high drag configuration, and limited > visibility, so the > sight picture during the approach is aggravated, by being blocked more. > Increasing airspeed will only undo what the slip is doing for you. Adding > POWER to > assist in maintaining the same airspeed may make it easier, but will make > the transition > tricky, especially if you happen to forget about the added power. > > There are two primary reasons that commercial aircraft crab way down > final, > and then "kickout" > into the sideslip touchdown: > 1) Passengers do NOT like to be pointed at the ground! That is a big NO > NO! > Big bank angles > when on final, or while descending is gaurunteed to get the "You can't > fly, > worst landing I ever had"! > remarks from de-planing passengers > 2) Many air carrier aircraft cannot lower the wing enough to compensate > for > the higher winds on final > and still clear the ground with the engines or wingtips. The volume of > buildings and surface friction > tend to lower the surface winds, so that the large plane can lower its > wing > enough during the "kickout" > procedure. So they crab until just before touchdown, then "kickout" into > the > sideslip to take advantage > of the slower windspeed, and quick touchdown where the wheels will take > over > directional control. > Thrust reversing and spoilers make sure that the aircraft remains > controllable by slowing quickly > and reducing lift even more. Since we don't have these devices, > "kickouts" > are tricky and not > recommended for lower hour pilots. > > Although it is a procedure that commercial pilots, even for single engine > rating are taught to add > to their bag of tricks, other pilots are normally not taught, and are > discouraged from using it. The > FAA prefers using what they call a stabilized approach. That is, crab for > correction at all times > while in normal flight, except on short final. When established on final, > and still at approximately 200 > to 300 feet off the ground, transition smoothly from the crab correction, > to > a wing low stabilized > attitude, and maintain this attitude with corrections as the wind changes, > until touchdown, and all > wheels are down, and then transition into the appropriate taxiing wind > correction until shutdown. > > Ken Jones: Thanks for the heads up! Went to the wrong FAR/AIM! Got to > throw that one away! > > Colin M Rainey > First National Mortgage Sources > Lending Solutions in All 50 States > 386-673-6814 o > 407-739-0834 c > [email protected] > > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to [email protected] > please see other KRnet info at http://www.krnet.org/info.html
