On 3/23/2013 11:43 PM, Wayne Paul wrote:
Tim,

This thread brings back a lot of memories of the advice I was given when I
purchased my first Schreder sailplane, most of which was erroneous. I only
had about 10 hours in a Ka-6E prior to purchasing an HP-16.

Snip

BTW, the HP-14 has the most powerful flaps of all the flap-only gliders.

Bob, do you really think a '14 with the flaps set at 90 degrees would float in
ground effect the length of a 4,000 ft runway?
http://www.youtube.com/watch?v=PXwy7dsLndM

Wayne
Moderator Yahoo hp-gliders news group
Webmaster Schreder Sailplane Designs website


My observational/PIC experience matches Wayne's claim above...i.e. I've never
encountered a flaps-only glider with more powerful flaps than an HP-14.

As noted elsewhere, my PIC experience includes C-70, HP-14 (short span,
long-flap version), & Zuni.

My observational experience adds 1-35 (retract & Club), PIK-20A/B, HP-16,
HP-18, AS W-20 (all have spoilers, but I'm referring to the large
flap-deflection versions here), Monerai and possibly a few more I'm forgetting.

As to the question, "[D]o you really think a '14 with the flaps set at 90
degrees would float in ground effect the length of a 4,000 ft runway?" my
short form answer is, "Yes." Reason? The "float tendency" is "excess speed
dependent." Every flapped ship I've seen and flown has exhibited similar
behavior in ground effect with full flaps...a *marked* decrease in apparent
drag and increase in "floating tendency." The more "safety speed" Joe Pilot
brings close to the ground, the (rapidly) worsening the tendency to float.
I've no idea how much "excess safety speed" an HP-14 might need before it
floated off the end of the runway compared to (say) a 1-35, and it would
certainly be more than required by a 1-35, but my takeaway point for folks
considering transitioning to large-deflection flaps-only ships is "excess
safety speed" carried through the roundout, likely won't be increasing their
immediate future's safety.

Like practicing inadvertent departures from controlled flight in the landing
pattern, my recommendation for carrying "excess safety speed for Mom and the
kids" in these ships, is; "Kids, don't do it."

That said, if anyone DOES find themselves floating undesiredly and rapidly
toward the far end of the runway in full-flapped ground effect, I'd next
recommend they simply begin reducing the flap setting as rapidly and "pitch
steadily" as possible, because their 3 remaining reasonably safe options are
now: 1) float with full flaps until the end of the runway or touchdown,
whichever arrives first; 2) reduce flaps/settle/touchdown/brake as heavily as
possible/groundloop if necessary; or 3) initiate the groundloop while still
aloft (Yech!). My recommendation is option 2, based on the float lengths I've
seen (always by other pilots) vs. the effectiveness of "typical glider wheel
brakes."

Stated another way, if conditions require "excess safety speed" (and any
transition-to-a-new-ship day, shouldn't), I'm a believer in getting rid of the
excess speed where it's safest to do so (duh! ;-)), which - IMO - in a
flaps-only ship is (for discussional purposes) in the "final 15 or so vertical
feet (and not the final vertical 3 feet). I never botched things so badly I
"dropped in" from a personal "fright height" either the C-70 (PIK-20-like
flaps) or HP-14. In both ships, even a botched (too rapid) roundout with full
flaps resulted in sufficient downwash from the flaps that - when I simply
halted my aft-stick movement the instant I recognized a "serious balloon" -
the ships ultimately settled to earth relatively gently. My guess is my worst
such "drop in" may've been from 2 feet or so, but I don't know. I know it
SEEMED much higher, but I never had anyone from the peanut gallery tell me
afterwards they thought I was going to bust the ship or my back.

The Zuni I did (twice? thrice?) "full-flap drop in" from sufficient height I
was worried for the ship...because - due to its relatively weenier flaps, drag
and downwash - it ballooned higher more rapidly before I caught it, and once
at the top of the arc, there's nothing one can do but (if sufficiently bold)
continue increasing aft force until critical AoA is reached, or, simply wait
(and count on downwash to cushion things...this is what I generally did).
Reducing AoA with forward stick "trying to maintain (reducing) speed" isn't
desirable. (Ask me how I know.)
- - - - - -

For anyone reading this while in a position of considering transitioning to a
large-deflection landing-flap-only ship, understand I'm touching upon
something that is completely - and entirely safely - avoidable simply by not
carrying "excess safety speed" in such ships. My experience - both PIC and as
a member of the peanut gallery - has been that none of the nuance expressed
above will be "necessary" if Joe Glider Pilot simply flies his approaches in
such ships using the usual "generally accepted by competent and knowledgeable
instructors" rules of thumb for choosing (in the absence of manufacturer
recommendations) an approach speed sensible to that needed to transition to
any new-to-him spoilered ship.

In broad brush terms, arguably the WORST thing a wannabe large-deflection
landing-flap-only transitionee can do - IMHO - is buy into "the intimidation
factor" so prevalent in the free advice world. Why? Because much of the advice
therefrom is not only confusing, contradictory and unnecessary, but actively
harmful.

Coupla examples spring immediately to mind (in no particular order)...
1) Big Intimidating Pitch Changes Required!!!
2) Not Enough Energy to Round-Out!!!
3) In Speed Lies Safety!!!
4) Reduce Flap Setting at the Risk of your Life!!!
5) Difficult to Judge Glide Path (because of pitch changes)!!!

I'm probably overlooking some others, but just to quickly attempt to provide a
measure of sensible counterpoint to the above canards...
1)Better not fly a Schweizer 1-34 or 2-32, then...
2) Utter rubbish. (I used to regularly fly "back of the polar curve"
approaches in my HP-14 in calm [e.g. late evening] conditions, and not once
felt I was marginal on roundout energy. In fact, the slower the approach, the
more time-available/easier-it-was to assess precisely when the final roundout
should begin.)
3) Discussed above.
4) Nonsense. Pitch falls out in the wash of airspeed control, regardless of
the ship being flown. (As noted elsewhere in this thread, vertically gnarly
pattern conditions in the weenily-flapped Zuni regularly occasioned the need
for this technique. In the [far more draggy HP-14] I once dumped full -
hydraulically actuated, "instantaneously"-dumping-by-air-pressure, flaps at
~300'agl on short final during a thunderstorm approach because I WAS going to
overshoot due to "cloud suck", and did a go-around. In my judgment the risk
associated with the overshoot (deep ravine on the west side of the old Black
Forest E-W strip) exceeded the risk associated with dumping the flaps, and the
low-starting-altitude go-around. By far the greater risk in the option I chose
was the go-around bit, not the flap-position-change bit, but at least a failed
go-around would have me contacting level prairie instead of a tree-studded
ravine. For the record, I never should have placed myself or the ship in that
day's position...)
5) More nonsense. (The steeper the approach, the easier judging one's roundout
point becomes. The time delay establishing the new, speed-stabilized
pitch/flight-path change coincident with your new flap position was probably
no more than 2 seconds in the HP-14 [whose flaps came down ~20-degrees per
pump of the hydraulic handle], and with each pitch down, the roundout point
became more easily identified..not that it ever was difficult.)

RAS is (probably) a lousy place to discuss stuff like this, but being someone
more inclined toward accuracy than toward "good hangar tale
hyperbole/inaccuracy," I occasionally feel the need to attempt to limit the
spread of less than informative, and sometimes outright unhelpful,
contentions. I'll go take my meds, now...

Bob W.