Cessna O1 / L19 Bird Dog

[eagleskinner]

I've been toldthat the bird dog is not easy to slip because of the sloping cockpit sides presenting so much flat surface that the rudder can't fight it. And yet I hear that in crosswind you should crab and control the slip with top rudder...

My question to the Birddog flyers then is "Can the bird dog slip? Or not"

Being only flingwing and Glider experienced, I don't have a clue, but I'd like to resolve this.

[stepwilk]

As I vaguely remember from my days of flying Cessna singles (other than the L-19), the basic warning/prohibition was against full-flap slips, something to do with airflow off the flaps blanking the...horizontal tail? Been awhile, but I don't think it had anything to do with the slab-sided fuselage, since actually a standard 182, say, would have even more side area than an O-1/L-19.

[eagleskinner]

That's something to think about for now - thanks.

[Lightning Mate]

All aeroplanes can and will slip.

[stepwilk]

Yes, but I was thinking in terms of whether or not they can be slipped safely, in this case with full flaps extended.

[Lightning Mate]

Another twopenneth:

Do not, repeat do not, sideslip a swept wing aeroplane. If it's straight-winged, you will probably get away with it. This is because the aeroplane manufacturer is more informed than you are, and will consider the results of uninformed "pilots" being stupid.

Sideslipping is a totally, totally unnecessary way of :mad: up and killing yourself, and is usually offered as a way of correcting a :mad: up approach.


With full (60 degrees) of flap there can be quite a bit of buffet in the elevator due to the disruption of the airflow over the elevators, if you get too slow and slipping it gets very interesting!


Excrement of male cow mate.

Get the approach sorted out early.

OK, challenge me anyone (suggest you don't).

LM, (Central Flying School. RAF). Bye Bye.

[eagleskinner]

Well... slipping in a Slingsby T21 was good practice and great for putting the fear of bejasus up your average "air experience" ballast. Our CFI enjoyed himself with airex and ab-initios and by all that's holy, when you're "looking down the wing" at your landing spot, you start thinking underwear.

OK - slightly urban there, but glider flyers know what I mean :O after all, a well executed slip gives you a good look at the ground ahead and under your nose (especially useful in an "out" landing and you want to watch out for surprises). But you are right, Lightning Mate - if you have flown the circuit properly, you shouldn't need to slip. On the other hand, a bit of hot air (thermal and not the CFI on the radio) on base and your pattern is shot - so you really do need to know how to slip - and I am sure that even a power plane can get thrown by a surprise gust or thermal.

I was just curious specifically about the Bird Dog's slips - after all, it has up to 60 degrees of flap and with a bigger donkey (260 HP+) it makes a marvellous tow plane.

Any tug pilots out there? I'll bet you slip a lot... it's all about getting down asap and hooking the next glider. What initiated this question was in fact just that kind of thought - i.e. would it be worth it to have a Bird Dog as a tow plane? A gliding club needs a good puller that will be back on the deck almost as fast as gravity will allow.

[eagleskinner]

Oh... anecdote time - and relevant to hot air in the circuit.

Kingsfield, 1976, Slingsby Swallow I think (God, I hated that bit** at first). Winch launch, figure of eight, no lift, not even off the ridge, so it was a case of "ho hum, eight minutes in the log book..."

As I passed the bus (our ops and tea room) my left wing decided to kick up. So hard that by the time I had even thought about levelling, I was 200 feet higher and and pointing back the way I came. Only one thing in a case like that - break the circuit. As I was still going up, I decided on the quickest way - keep the turn on.

You know Kingsfield? Cyprus. Three or four turns later I was at 6500ish over the military hospital with the silver height gain being written into my logbook. I still have the baro trace somewhere - the up-curve is so fast, it is sloping backward.

Couldn't have completed that circuit properly even if I'd had full spoilers and slip on. That was not a thermal, but a bubble of hot air.

Could have been the Oly2b... I really must see if I can find that old logbook.

[eagleskinner]

Hi Ed, Interesting... I have been towed by a Supercub and that was indeed phenomenal. Behind an Archerokee it was always a case of keeping your glider down so that the tug wasn't hampered. Behind the supercub it was a case of doing your best to keep up - God did those supers pull (by comparison). They even made short work of the Bocian!

It's easy to imagine, then, another eighty horses in a stripped Bird Dog. Pawnee...? Heavy tank? But I did read somewhere that they make good tugs with a four-blade. Even though they were built for ag-work.

Mind you - my best tow was behind a Super Chipmunk - but what a waste. It's like putting Arkle and Red Rum in the traces of a milk float.

Anyways... slipping the dog...

[kluge]

Sideslipping is a totally, totally unnecessary way of up and killing yourself, and is usually offered as a way of correcting a up approach.

er try flying an approach in a Pitts Special without a controlled side slip - even without a x-wind. Bit hard to see the runway without exceeding Vne :eek::eek:

Have to recheck my old pilot notes but I recall that a side slipping approach for this a/c is SOP.

Here's some readily available background

http://en.wikipedia.org/wiki/Slip_(aerodynamic)

Granted a little different that EEs finest but always challenging in its own way.

[eagleskinner]

Funny how coincidences happen... My monthly subscription of "Flieger Magazin" arrived the other day...

...with a good feature on sideslipping. The author goes into the reasons why in some detail and expleains why it is taught, how a slip works, how the wing profile changes (stretches) and quite a lot of scientific background. The mag also published an accident report about a glider pilot who came in too high and tried to lose height by circling (in the pattern? How cool is that, not?) Unfortunately his airspeed control failed him and he dropped off a wing, crashing fatally less than 200 yards from the threshhold.

I don't really believe in coincidences as such, but they are fascinating to observe and wonder about.

But the verdict among my GA and glider friends is that slipped approaches are a "must know" and "must practice". Swept-wing and fast mover drivers may well have a totally different view - especially with twin lateral intakes where the "trailing" intake may be starved and the engine die, along with all the other coincident aerodynamic issues that may make a paraffin heater fall out of the sky in a slip, but for many aviators, a sideslip is good practice.

So... where are all the BirdDog drivers? :hmm:

[barit1]

Lightning Mate:

Another twopenneth:

Do not, repeat do not, sideslip a swept wing aeroplane. If it's straight-winged, you will probably get away with it. This is because the aeroplane manufacturer is more informed than you are, and will consider the results of uninformed "pilots" being stupid.


Here's my own experience cross-controlling a PT-22 (http://www.pprune.org/flight-testing/392357-evaluating-stall-characteristics-best-procedure.html#post5253367) about 45 years ago. It had a minor amount of sweepback, I'm told to accommodate a change in c/g from earlier versions.

[SawThe Light]

"never sideslip a swept wing aeroplane"

Just as well that Air Canada pilot didn't know that when he landed at Gimli a few years back.

[barit1]

Realistically speaking, you slip to kill excess energy (you are hot and/or high). Keep the nose down, respect your Vref, and slip away.

Best to practice this at a generous altitude, find out what the airplane likes or doesn't like, then don't hesitate to use it when appropriate. While he probably didn't have that luxury, the Gimli 767 captain got it right.

[Jeff Glasser]

When flying our Skydive clubs Cessna 185 I would side slip it if high on the approach, never a problem, and I never experienced tailplane/elevator buffet doing this.
The only time you could experience elevator buffet was with full flap and the elevator trim right back. We would always wind a few notches forward after winding it all the way back after selecting full flap on the descent, this would stop the buffet.
I also prefered to 'wheel' it on as it had a tendency (o.k. it was me) to bounce.

Jeff

[Jeff Glasser]

I was'nt infering they were the same edsbar, just throwing in my two pennath about buffet.
I know very little of the 'Dog' only once having been close enough to one to stroke it and lick it!!