They got the gear up very early while still being over the runway. That shows that they where aware of the situation pretty soon.

Anyone know if #1 prop was feathered at any point,and, if the aircraft used water/water-meth. injection...?

Hmm, could be, but my recollection of flying in the piston era was that the gear coming up early was fairly standard.

You'd select gear up as soon as you had a positive indication of climb. That's usually over the runway.

On a South African forum it was reported that they had planned to use water/meth for this take off. Apparently this was infamous for causing backfiring leading to the auto feather engaging so many crew didn't arm the auto feather. The use of water/meth could well explain the popping we hear on take off. They also had a habit of exhaust system fires aft of the engine.

Looking at the vid from the Cessna I would guess that they had both engines running until they turned onto base considering the speed they were doing. Something happened on the base leg for them not to turn onto final. May be they shut down the engine and it wouldn't feather.

Most likely Cylinder head cracked then blew off thus constant smoke out one exhaust on that cylinder side. If it dropped a valve it will maintain power at 30 inches or barometric but will PUFF Smoke not stream smoke. If smoke trailing from both exhausts it is a blown supercharger drive seal or broken supercharger drive the later will have the engine stop and windmill, if it breaks the front reduction gearbox gear may end up with a run away prop.
With blown off cylinder head you can in emergency keep running the engine at higher power (or barometric if its banging to much with the blown cylinder ) which is what you maybe seeing going on from the Cessna video and the takeoff. It shakes like hell for few minutes but will put out until the piston comes apart, breaks the rod at which time you feather it . Sometimes will run 1 minute sometimes 2-3mins dependent where the cylinder head comes off. Had 8 failures myself with R1830-92 and R2800-CB16s. 1 Master rod, 1 rod, 2 dropped valves the others were cylinder head blew off some through the cowl. When these big radials stop suddenly from seizure other things break and shear it is a lot of mass and moving parts
All my failures on takeoff or first stage power reduction. All at sea level and that was bad enough. Just some technical thoughts but the investigators will advise later.

They did a good job with what they were given on the day, speedy recovery to all..

amazing, 8 failures would give you grey hair, thank goodness for the jet age

Sorry to be pedantic but at, or soon after rotate the VSI, depending on the type of aircraft may well give erroneous readings. As correctly pointed out above, a positive climb is reliably indicated by the altimeter.

Sounds like an Old Wives Tale. Flying the Convair 440 I have used ADI on hundreds of occasions. Not once did I experience back-firing on take off. Certainly we experienced occasional rough running due to spark plug fouling with 115/145 Octane fuel but it usually cleared itself during initial climb. As far as I recall autofeather was armed for every take off. .

Positive Climb
 

I do not dispute the point regarding erroneous VSI indications, however the call often is "Positive Rate, Gear Up"

Only airplane with a radial engine I have ever flown was a T-6/Harvard (also in South Africa). Of course that is no airliner and it has plenty of power.

Anyways, from your experience would you rate the climb while over the runway (and of course still accelerating) as normal for these kind of aircraft? Of course the density altitude of at least 5,000ft (not sure about the OAT that day) plays a big role, too.

I am just interested if they still had power from the left engine at that point. There is no visible yaw and no bank towards the "good" engine but unfortunately you can't see the rudder on the video or any of the pictures after lift-off.

Does anybody know the blue line speed of a CV-340?

I had never heard of ADI causing backfiring either, at least not a properly functioning system. I did have one incident where I rejected a takeoff due to backfiring and it turned out to be a ruptured diaphragm in the ADI regulator. However that problem made itself evident as soon as the throttles were pushed up far enough for the ADI flow to start. WE didn't arm auto feather, but it was only required for takeoffs over 100,000 lb, and our operations were relatively short legs so were were always landing weight limited, so never needed to depart over 100,000lb.

Meaningless semantics. A Positive Climb is inherently also a positive rate of climb. The SOP call at my current airline is "Positive Climb"

Post WWII most piston airliners were certified on 115/145.

On 100LL derates have to be applied. Engine out performance on 100LL will be less than on 115/145.

Same as in my company: I believe it's an Airbus standard call out. Also in our SOP, the '' Positive Climb'' call out is based on RA, not on VSI or altimeter as both will increase while the main gear are still on the ground.

My time radial engined airplanes was all in far northern climates at close to sea level. Given that this was, as you say, a much higher elevation and possibly warmer OAT I wouldn't consider the low initial climb extraordinary.

As someone else noted earlier, it is quite possible for an engine to have a cylinder failure and still be producing a substantial amount of power.

I haven't flown the Convairs, but I'd expect that it didn't have a blue line, but rather V speeds which were calculated based on takeoff weight, altitude and OAT. Blue-line is more light twin figure. It's possible though, that era was kind of a transitional period for aircraft performance theory.

So it would rather be V2 then, like with a jet. Anyways, the numbers would be interesting. They seem pretty fast passing the 172 in the 2nd video.

Not exactly true. The R2800 CB16 engine was certified on 100/130 for which 100LL is an approved alternate with no reduction in power. the CB17 was certified on 115/145 and would develop an additional 100 HP The Convair 340 may have had several different model engines installed, including the CB16 and CB17

That was, what I was thinking of. There is no yaw visible at all. Even if you react very quickly I would expect at least a little yaw at low speed and high power.

Yes, power had to have been developed at least right after takeoff as the rudder is faired in the video as the aircraft passes overhead and away from the camera.

Correct. In the video that shows the T/O from behind the runway you can see that there is no rudder used after the A/C overflew the camera. Power seems to be evenly distributed.

There is now a video circulating taken from inside the aircraft, left side, with the rear of the engine in view. The video continues to and beyond impact.

Taken from inside.

While not wishing to speculate or pre-empt the investigation into this tragedy, the following personal experience of what can happen when an aircraft has been out of service for a protracted period may be worth relating.
In early 1993, I was contracted to ferry a Vickers Viscount from the USA to Zaire, This was an early 700 series that had been a VIP machine for some of its life, so had relatively low hours. It had been on a storage maintenance program in the Arizona desert. They had kept enough fuel in the tanks to carry out periodic engine runs. When we took delivery and did a short test flight I was pleasantly surprised at how all the systems except the autopilot seemed good to go.
We refuelled to full tanks to position from Tucson to Mena, where we would fit extra ferry tanks. About two hours into the flight the number one engine ran down and autofeathered, quickly followed by number two surging badly. A quick right hand turn and down we went towards Ardmore, noting all remaining fuel flowmeters were fluctuating.
At shutdown it was found all four fuel filters were badly clogged with rubber deposits.
Having been baking in the desert for so many years, the tops of the fuel bladders had badly perished. It was OK while a small amount of fuel remained in the tanks as it kept the lower sections moist enough not to leak. But once we went to full tanks the fuel sloshing around washed the rotten rubber into the system.
Could it be that this model Convair has rubber tanks, or rubber fuel lines? An engine running at high power suddenly leaned out due to fuel blockage would possibly backfire badly. This could cause a supercharger fire with no immediate loss of power, so no noticeable rudder input. Or a dramatic loss of power on both engines could explain the rudder position. Another possibility is a rotten or burst fuel line could have caused the fire, and the fire could have damaged the aileron circuit.

In looking at the internal footage a few notable observations are apparent

1, sooting on the panel junction in front of the exhaust outlet, and 2 fire under the wing - which is definitely abnormal and extremely alarming.

It would be a presumption that a fire has broken out, at some stage, either between the engine power section firewall and nacelle firewall, or a mechanical failure has occurred with the engine power section(Cylinder or multiples of, or rotating elements) and an uncontrolled oil leak is igniting on the exhaust and exiting vial the cowl flaps - which there would be no fire suppressant for(reserved for the Accessories section - oil and Fuel services etc).

In the departure video there is clear flaming in the exit area of the augmenter, which indicated something mechanical is amiss in there, the popping of the engine, smoke and strobe effect of the video indicates RPM changes occurring, and waiting for the Governer to assert itself - rpm recovery. Im going to assume the later - if you have a fire in the accessory section, fire alarms would sound, the engine(if determined is overheating/or on fire) would be secured and extinguishers used - Securing of would cut fuel and oil supplies and stop pumps for doing just that - The propwould also be feathered and stopping rotation.

A failure in the Power section may produce a fire that cant be seen, and if still producing power may lead you to continue until safe to secure. As for landing in a paddock - there are two pilots who will know the events relating to those decisions. Mine is but speculation, I am willing to speculate that they may have been made aware of an external fire late in to the flight and decided being on the ground in a controlled fashion was a better outcome. than pushing on to the runway.

Ordinarily I would have thought that this crash was unsurvivable, looking at the pictures. I am inclined to agree with an earlier post that this craft was "crash landed" rather than "crashed", that is it was under control. Another reason for the high survival rate is the incredible strength of these old birds. I sure would not have liked to see a plastic fantastic composite aircraft after an arrival like this.

The pax, to the best of my knowledge were aviation people or the family of aviation people so much more likely to stay calm under the circumstances.

I suspect the P.F. had a bootful of right rudder. Which would be consistent with power loss on the port engine. How much aileron needed to control the aircraft laterally, hence crossed controls is anyones guess. I also suspect the prop was not feathered for whatever reason, at or just before impact looking at the rotating prop in the clip.

The upward aileron puzzles me, it was not in T/O or shortly after. It looks like it is jammed full upward. It could indicate they could not crank the plane in a right turn to join final. To me it looks like the nr1 continued delivering power. The last sec before impact You hear the engine(s) roaring up.
If the jammed aileron proves to be the scenario, they have met a miserable set of emergencies. For the sake of the investigation it would be nice that they could remember a few things but for the sake of their mind it would be good if all after T/O is erased. So they will not end up waking up now and then from a nightmarish dream the rest of their life.
I wish them a good recovery.

Theres a surge/power change at 43-44 seconds as well. It actually sounds like a reduction or miss then returns quickly thereafter.

The upward aileron could have been a momentary turn of the control wheel taken by entire coincidence at that split second the camera shutter operated. I guess the question is why the prop was not immediately feathered but allowed to run during the entire attempted circuit - particularly as a fire in that engine was noticeable to the passengers. No doubt there will be a logical explanation to be revealed during the formal investigation.