dc3 stall characteristics

[mstram]

I've read, and been told by a few pilots that the DC3 has very nasty stall characteristics. This apparently is the main reason to "wheel-land" the plane.

What makes the stall so evil in this plane?

Why was it designed that way? I'm guessing comprimises had to be made somewhere.

Mike

[Reverend Doctor Doug]

Whilst by no means an expert, I have flown a couple of stalls in the Dak and I can tell you they get your attention. The end result is a huge nose down pitch (probably 40 deg or more if memory serves) accompanied by a significant wing drop. Why it does this I cant remember, although I'm sure I was told. Maybe the eliptical type wing (just a guess). Some of our aero wizards should be able to elaborate.

The rev

[mstram]

>Would it be because it is a big tail dragger with a relatively low stall speed? If the main wing stalls before the elevator, the plane will nose down and as the c of g is behind the main wing this makes the dive more exaggerated than an aircraft with a forward c of g?

I think you're a bit confused about "taildraggers" and c.of g.

The g.c is *not* behind the main wing ! If it was the plane would be incredibly unstable in the air

The c.g. is behind the main *wheels* ! Which like any tail dragger makes it unstable while on the ground ! , that is unstable directionally as a "ground vehicle".

[Cargogirl]

I can still remember this discussion from my initial ground school for the DC-3.

You are correct about the design of the wing being the cause.

If you look at the airplane from overhead (or underneath) it is indeed a swept wing airplane. If you recall where the stall begins on a swept wing aircraft then you'll see why the DC-3 likes to try to roll over on you during a full stall.

Our company prohibited us from doing full stalls in the airplane, and after having been through one during a training flight with a new hire, I know why!

:eek:

[pigboat]

The Rev and Cargogirl have got it right, I think. It's due to the shape of the wing. It also doesn't have a stall warning system - no bells, whistles, lights or stick shaker. It's been awhile, but I seem to recall that it took a lot of muscle to horse the airplane into a stall unless you had a lot of nose up-trim, and there was a clear pre-stall buffet. At the break the pitch down and roll was impressive though. :D
Interesting note, on skis the airplane is very nose heavy, so much so that we used to use the rear tanks as the mains. The skis weigh around 1100 pounds total, and empty the c of g is at or very near the forward limit on the pure freighter version.

Cargogirl, does Folsom's still have that one on floats?:cool:

[Cargogirl]

The last I saw Folsom's DC-3, they were having the interior redone in Bangor. From what I understand, they were going to take it to Florida to place it in a museum.

Because of the aircraft/float combination on that bird, it was in the experimental catagory, and they were unable to use it for charters, which I believe was their original intent.

It will be missed at the Greenville Sea Plane Fly-In, I'm sure.

Cargogirl

[Centaurus]

The clean stall in the DC3 was pretty conventional for an aircraft of that era - lots of pre-stall buffet and some wallowing. But the full-flap, power-on stall was really something else.

My job as a QFI in the RAAF was to convert newly graduated pilots with a total of 210 hours (all on singles) on to the Dakota as their first multi-engine type. When stalling the Dakota in the dirty configuration, it shook up these new pilots (and myself) when the aircraft would try to roll inverted if you failed to take immediate action to prevent further wing drop. Inadvertent use of aileron to pick up a badly dropped wing would only upset the beast more. If I recall, you could lose around 1000 ft during the recovery process in a full-flap power-on (15 ins of manifold pressure) stall.

The Dakota was never a natural three-point landing aircraft. Not like the Lincoln which was a purist's aircraft for three pointers. The Dakota elevator would over-balance as you got near the three-point attitude and this could result in the tail-wheel touching down just before the main wheels. If that happened, the aircraft would quickly swing and one needed to be real nifty on the brakes and rudder to straighten up.

A tail-high wheel landing was relatively easy to perform and was a must in any cross-wind. It was fun to try for a three-point landing in calm winds, but not worth the trouble of keeping it straight after touch-down if you cocked it up. The wheel landing technique had nothing to do with a possible wing drop problem with three-pointer. It was more to do with a damned uncomfortable feeling on the elevators the longer you held off to get the three-pointer.

The most dicey event I had on a Dakota was when the rubber de-ice boot which went along the whole of the leading edge of the wing, suddenly split asunder just as the gear was selected up on take-off. We got around the circuit with almost full aileron and a fair bootful of rudder and did a flapless landing as we were concerned that lowering of flaps may have made the roll situation worse.

Fortunately we touched down just as we ran out of full aileron control. The de-icer boot had split horizontally along the wing from the landing light to the wing tip and the loss of lift felt just like an engine failure on that side. An interesting day.

[John Farley]

Interesting thread.

During 1998 Atlantic Aeroengineering at Coventry modified a DC-3 as a Radar flying test bed for the new Racal (now Thales) radar for the RAF Nimrod. This involved fitting a very large radome under the nose of the DC-3 making the front of the aircraft very reminiscent of the back end of a dog.

This extensive modification naturally had implications for handling and performance and required the aircraft to be flight tested to restore its type rating. This testing included full stalling trials. In such circumstances, elderly aeroplanes have to meet not today’s airworthiness standards, but those that applied at the time of the type’s initial certification. In this case as spelled out in an FAA document of 1932 vintage.

While planning the trials I noted that the 1932 requirements required stalls to be carried out in the landing configuration at up to 75% power. When I talked to Atlantic’s training captain on the DC-3 he said they restricted power-on stalls to 40% or less to avoid very large wing and nose drops. He felt we could finish up inverted if we tried them at 75%. Accordingly given this sage advice (I had not flown a DC-3) I asked the CAA for an exemption from meeting the 1932 paperwork. They said we could put whatever limits on the trials that we wanted but they (naturally) would not necessarily certificate the aircraft based on such restricted trials.

Off we went and at 40% I found that at the stall there was a slight tendency to drop the left wing, limited to about 10 deg. We went on to do the 75% stalls with no wing drop but a slight un-commanded nose up tendency.

Why so? Simply because the aircraft was flown to reduce speed very slowly at not more than one knot per second, and no attempt was made to control the rate of climb or descent while this speed reduction was going on. The wheel was used to trickle back the IAS, so as soon as any symptom developed a slight check forward was all it took to take the wing away from the onset of the stalled condition and put a stop to whatever was going to happen.

Clearly such a technique produces very different results from just pulling back and holding level flight until something uncontrollable happens. Flying like that the speed reduction is likely to be quite rapid and so the wing will penetrate to an angle of attack way beyond the start of the stall before you have a chance to do anything.

Once the boundary of the first stall symptoms have been established, it may be acceptable to deliberately continue the backpressure on subsequent runs to progressively investigate the likely effects should somebody penetrate way beyond the first stall symptoms.

Bottom line – IMHO the DC-3 is no different from any other aircraft, if you charge into a stall you may get quite a surprise. Tickle it gently with some feel for what you are doing and it will talk to you with the odd twitch of the ailerons, a bit of buffet, a slight nose up movement (knock it off at once if you get one of those) or a nose drop, or a gradual tendency for the nose to move out to one side or combinations of such things, depending on power and configuration.

When we plotted my stall speed results, they were 2 knots faster that the book for the unmodified aircraft. I explained to Atlantic’s chief pilot that if he flew the aircraft using my technique he would doubtless get two knots slower than me because he was younger, knew the aircraft very well and was very current. And low it was thus and it came to pass that the CAA were happy.

Off topic, I favour the flight test stall technique for instructional purposes as well, at least with apprehensive and inexperienced students who can easily develop a real concern about stalling if pitched in to a fully developed stall right from the start

[mstram]

Thanks for all the great info and stories everyone.

Mike

[pigboat]

CG, thanks for the info. Too bad they were unable to certify the thing. I believe that is the original military C-47 that was on floats during WWII. I remember an article in Air Classics on the work they did to get the aircraft operational. Incredible.

John, we never did any stalls with full flaps, just one quarter flaps and around 18 inches of MP, as I recall. However we waited 'till we got the break and the accompanying roll before recovering. We always used tail low wheel landings, never three pointed it even on short strips or on skis. In a crosswind it was full wheel landings and then just a nudge of forward stick to pin it on. On ski take-offs, the normal procedure was to add one quarter flap after the tail came up, and then ease the thing off. I seem to recall the airspeed would be around 70-75 kt or so, below VMC, anyway. We also used that technique if the dirt strips we operated out of were sloppy.
Another company here operated three DC-3s with the Goodyear x-wind gear installed. I never got to fly one of their machines, but did jumpseat a couple of times. The last item on the pre take-off checklist was to caster the gear, and in a crosswind you'd be looking down the runway from the dv window. A real pecker of an operation. I always thought it defeated the basic rules of aircraft handling.:D

[John Farley]

Pigboat. Very interesting. I can’t imagine what it would have been like with castors!

Sounds like you handled all touchdowns the same as I did.

Actually, these elderly aeroplanes do need a fair bit of stick and rudder skill, but that was the norm in those days and nobody thought much about it. Modern aeroplanes need fewer handling skills but a lot more thought and care to operate in today’s ATC and regulated environment.

Regards

[Centaurus]

Wonderful reading - also thanks JF for your stall explanation. I think we were a bit amateur in those days, despite having a lot of time on type. Certainly we did not approach a practice stall at a measured rate but nor did we pull it straight up to make it stall faster. But your point is well taken. I do know that the powered on wing drop was a well known characteristic found by many squadron check pilots.

At one point in my life I was flying 737's for a living and doing the odd moonlighting trip on night freight DC3's. It was common practice then to engage the autopilot while taxying to help stop the rudder from flailing with a tail-wind or crosswind. It meant having to use differential brakes to keep it straight down the taxyway. The rudder became rock solid with the autopilot engaged. Probably not good airmanship in retrospect but better than risking breaking various cables which could happen if the rudder was allowed to inadvertently bash from one side to another.

During a crosswind landing I had barely touched down in a tail-high wheel landing and was just correcting for a slight swing when the rudder locked up. It was a bit dramatic because without rudder one had to use quick brake application to keep straight. The gear warning horn sounded a couple of times as brake correction was made to stop the aircraft going off the runway into the crosswind. Having slowed down and being unable to apply any rudder, I looked down and was astonished to see the autopilot knob engaged.

I asked the other pilot (an old and bold with a squillion DC3 hours) what the hell was going on? He said that he thought I might like to have the autopilot on after landing to stop the rudder from swinging about. So the silly old ****** had leant down and engaged the autopilot without saying anything when I had just got the thing on the ground.

Another time a couple of CFS pilots were practicing asymmetric flight at altitude. After closing down one engine and feathering the propeller, the shut down drill was continued by pulling the firewall shut-off handle which cut off fuel, oil, and hydraulic fluid.

After a bit of manoeuvring here and there, the engine was restarted and a few minutes later, the other engine was throttled back to zero thrust while the previously feathered engine was used to do a single engine go-around at altitude.

Shortly after take-off power was set on the live engine all hell broke loose when the engine seized and threw the propeller into the fuselage. It passed less than a foot behind the co-pilot cutting the fire extinguisher bottles in half (they are situated immediately to the rear of the co-pilot's seat) - and climbing up the fuselage leaving a huge gash. The cew immediately applied power to the remaining engine which had been at zero thrust - only to find that the departing propeller had also cut through the engine instrument lines resulting in crazy readings on the live engine temps and pressures. The aircraft was landed safely.

Investigation revealed that when the firewall shut off handle from the previous feathering drill had been pushed down and reset, the geometry of the cables was such that the hydraulic and fuel shut-off lines had reset but that the cable to the engine oil did not. Thus it was not long before the engine seized at take off power with no lubricating oil supply.

[galaxy flyer]

Holy Necromancy, John. :ok:

GF

[pattern_is_full]

As I recall, from the TV documentary Planes That Changed The World - DC-3 - the original DC-1 paper design and wind-tunnel models had wings with taper but no (or minimal) sweep. Perpendicular leading edge and angled trailing edge.

Wind tunnel tests revealed stability problems that the math hadn't predicted, resulting in a major redesign, including adding the sweep (and the fillet or fairing at the wing/fuselage junction, and numerous other tweaks) before the DC-1 prototype and DC-2/3 production aircraft ever flew.

Before: http://caltech.discoverygarden.ca/islandora/object/ct1%3A685/datastream/JPG/view

and after the changes: http://www.airminded.net/dc3/dcwindtunneltest.jpg

[JammedStab]

Now here is a DC-3 stall, and a whole lot more.

https://www.youtube.com/watch?v=EFyyLbD-Y7o

[Jwscud]

Thanks for bringing this back - JF's post on his approach to stall tasting was fascinating reading.

[ShyTorque]

SlQZJcAoERg

[Mansfield]

Squirreled away on my website are two old icing accident reports that may be of interest. Both involve DC-3's, obviously, and both investigations conducted some flight testing with associated discussion of the DC-3 stall characteristics. Pretty interesting for a variety of reasons, but may be of use to this thread.

http://flightopsresearch.org/data/files/united21.pdf

http://flightopsresearch.org/data/files/northwest5.pdf

[con-pilot]

While it has been some time ago, over 30 years ago, I don't recall anything about the stall characteristics of the DC-3 to be all that exciting. However, all we had been trained to fly the aircraft to was the approach of a stall, then recover and move on. It seems like the aircraft gave plenty of warning if you knew what to look for. I also remember the approach stall series, part flaps and partial power in a bank to be the most dramatic, as the aircraft would roll off toward the low wing and the nose would drop. Never the less if you started the recovery as soon as the wing started to drop it was a quick recovery. But it taught you to never get into that condition anywhere near the ground.

The DC-3 was/is very easy to fly as long as you respected it, which I did. I respected every aircraft I flew and the more I gained experience in any given aircraft, the more I would respect it.

As for icing, there was only one icing event encountered by me in a DC-3, as our DC-3 had no de-icing boots and we avoided any actual or forecasted icing conditions. Except for one night we came home late and encountered unforecasted icing. The accumulation of ice on the wings didn’t cause any problems, it was the instant ice covering the forward windshield that caused problems. We had removed the de/anti-ice windshield equipment as well.

So I was forced to open the little direct vision window in the forward windshield and the side sliding window on the left side so I could see out to land.

I think my nose and left ear finally thawed after my third or fourth Scotch that night.

[Centaurus]

https://www.pprune.org/tech-log/89061-dc3-stall-characteristics.html

Thanks for that link Sagan. A pity that students and their instructors at flying schools are not encouraged to use these Pprune pages as an invaluable insight to airmanship knowledge rather than be buried in the bureaucracy of Part 61 and M o S

[vilas]

I can say I have done a lot of stalls in DC3 .It is more than 50 years now but I have flown DC3 in Himalayan mountains for supply dropping for maintenance of military posts. Also we had some airstrips by river banks called Advanced Landing Grounds layed with PSP or Perforated Steel Plates. In Air Force we always did what's called three point landing but our civil counterparts did two wheel landings. We used to also spent some time with the aircraft maintenance company testing DC3 after major maintenance where for more than a month I have done stalls virtually every day. I didn't find anything particularly vicious about the stalls. There was noticeable judder and nose drop. But I don't remember any serious wing drop.

[Centaurus]

Slight cross purposes due Forum drift for want of a better term. Possible finger trouble by Centaurus.. Humble apologies. . See: https://www.pprune.org/pacific-general-aviation-questions/635522-wing-drop-some-wartime-aircraft.html

[rigpiggy]

Is the Turbo Dak with the wingcuffs a better staller?

[ehwatezedoing]

Is the Turbo Dak with the wingcuffs a better staller?
It seems so... I don't recall any massive wing drops on my initial training. Recurrencies in Canada are only approaches to stall and recoveries.

The Basler have a weird aerodynamic characteristic of its own though....You can literally lock your rudder in full deflection during a sideslip, mainly due to the airflow around its square cowlings. I was warned about it but it still felt strange pushing one pedal to its stop, removing my feet and not seeing that coming back neutral (while still holding the ailerons to counteract)
This aerodynamic oddity is easy to break.

Not sure why the FAA let that slip during its certification.



I think Pilot DAR flew the type and may have some input to that.