DC-3 high-speed ground loop
By Robin H. Anderson, Captain (Retired)
In the late 1980's I was flying for Interocean in Mozambique on their mixed fleet of nine machines, featuring DC-4, DC-3 (C-47) and DHC-4a (STOL Caribou) aircraft, on a UN food airlift programme through LAM (Lineas Aereas de Mocambique) after the 'supposed' ceasefire between Renamo and the Government forces.
This was a semi-mercenary operation in terms of employment in as much as you flew with some very in-experienced co-pilots - one pulled the mixtures back after takeoff in a Caribou instead of the pitch levers! You flew from dawn to dusk, carrying maximum payloads for only $5/hr. more than those same co-pilots under trying conditions, on a twenty-one day on and seven days off basis - cooking your own carried-in food from the RSA at outstations - such as Quelimane and Chimoio and even at the base house at Beira. You did this until the next 100hr. inspection was due or until fuel and oil had to be flown in from Beira.
One was always battling to get refuelled during the day as the hand-pulled tank trailer and drum pumping was time-consuming and there were plenty of light aircraft using the same facilities. Still, that $25 an hour was a big improvement on the R11,55/hr. (About $20 in those days.) gross that I had averaged flying Luxair (Trek) Boeing 707s over five years; so the incentive was there to accept the downside - You would not have been invited back if you had not! – Much later, however, we found out that LAM was allocating Interocean $100/hr. per crew, but our local manager had been splitting half with the owner, Mr. Harrison!
One did everything possible to keep on operating even though you picked up the odd bit of flack from ground forces ! We even developed different approach tactics to allow for the weak brakes, for which we were told there were no spares, and I had landed at Caia and other short fields many times without using them as a result. I don't mean by 'hanging on the props.', either !
Coming into Caia on the Zambezi early one morning from Beira I had let fellow captain John Wilkinson fly the DC-3 from the left-hand seat after he had done some flights from the right, to get current again. He had checked me out on the four tonne payload Caribou, which was a small Hercules type machine, but with two radial engines. He had at that time some 10,000hrs. on the Lockheed Hercules (C-130) alone!
At 85 knots on final to runway 09 I called for him to reduce his speed, with no response from him, and shortly thereafter to, "Go around John, we'll never make it!” We touched down well in at high speed on this short but wide tarmac field and getting on to the brakes as well, I ran the pitch to full fine calling for him to get the tail wheel lock out. "I've got her John, but keep on braking" I said and settled the tail wheel on the ground, staying in the centre of the runway, leaving full flaps down for aero-dynamic drag. By this time the riverside runway end was looming up and just as it disappeared under the nose I called, "Brakes off", but kept my left brake on as I belted the right engine to 48 inches boost and we came around smartly, releasing the brake.
We felt NO RETARDING EFFECT as we skidded sideways and almost immediately we were facing 180 degrees to our landing direction - but, were moving straight down the centre portion of the runway backwards, despite the power from the starboard engine!
(This indicated that the friction on the tyres in doing the 'groundloop' had not reduced the forward inertia appreciably and thus had not placed undue strain on the undercarriage. The geometry of the tail wheel fork and wheel is such that the inertia and weight of the heavily loaded aircraft kept it aligned in the centre of the fuselage in the opposite position to normal. So had this been a single-engine landing I would have had to use the right brake now momentarily, and push the control column full forward to lighten the tail with 'propwash' to hopefully allow of continuing the turn to the left in ever-slowing circles.)
In the event, by bringing in the power of the port engine to match that of the starboard, the landing inertia was cancelled out and we began moving forward as we felt the tail wheel fork 'wiggle' the tail as it assumed the regular forwards trailing position - the fork, in passing 90 degrees to the fore and aft position made the tail empennage feel higher off the surface than the 180 and 360 degree positions, explaining the tendency to remain in these trailing positions at relatively slow speeds. Retracting flaps and opening the cowl flaps whilst throttling back the engines I parked on the spur to the right and allowed them to cool below 170 degrees before shutting down. Disembarking we both went over the tyres and u/c looking for damage, but apart from some scuffing around the whole of the tyre circumference on both tyres, we could not see anything untowards.
Walking back down the runway towards the one black skid mark in the centre, John said, "I liked the way we handled that one!" and to say the least I was flabbergasted! We paced off the skid which measured 7 meters and there were no pieces of rubber lying around. Just the one black skid mark much as if a wheel had locked up on heavy braking. The tail wheel had luckily not gone off the wide runway otherwise it might have sunk into the rain-softened earth and the aircraft would have continued skidding sideways until it stopped! Not good! (...but in hindsight another possible way of stopping in an emergency!)
We had three metric tonnes of maize in 60 x 50 kg. bags plus about seven hours fuel on board, so the tail wheel would never have been able to ride up over the relatively high vertical solid edge of the tarmac to allow the turn to continue. Examining the runway surface it confirmed that the loose gravel thrown up by departing aircraft at this far end had further helped to alleviate the friction on the tyres along with the reversionary liquid rubber from the treads themselves, thereby reducing the strain on the dual-cantilevered oleos of both wheels, as we skidded sideways.
This was confirmed later when back at Beira base, Mike Cunnynghame and his engineers gave the undercarriage a more exacting inspection and found nothing wrong. The subsequent takeoff and landing at Beira had obliterated all traces of scuffing on the tyres, we found! We continued flying the same C-47 that day and achieved a goodly tally of trips.
Within the year John was sadly to perish in his beloved Hercules in Angola when it was hit by a missile.
The accompanying pictures illustrate the outcome previously of a different 'Ground loop' by the chief pilot, in the reverse direction, also at Caia. This had caused me to think more seriously about Dakota 'Ground loops', and formulate a plan. He had left the runway to starboard about two thirds down and tried to make a wide turn to the left, but the tyres had dug in to the soft sandy soil and brought the machine to an abrupt halt; with the results pictured.
C9-ASQ "Little Annie"
After ground loop at Caia in Mozambique
Photograph: Cyril Kemp
After ground loop at Caia in Mozambique
Photograph: Cyril Kemp
You will note that whenever possible this manoeuvre should be done to the left as both propellers rotate clockwise and a blade tip or even the whole propeller can end up coming into the cockpit should it hit an obstacle under power. Also this is a POSITIVE manoeuvre and should be done RAPIDLY to minimise the time spent skidding broadside-on to the runway. Based on keeping the Dakota on a relatively firm surface, I venture to suggest, that performed as we did having this LAST RESORT action in mind, if the need ever arose, could reduce the incidence of undershot landings on short runways, and over-runs.
For my part I was prepared to use it on aborted takeoffs, no matter which engine had failed, if stopping was a problem. I have often wondered since if Donald Douglas and his team had ‘ground loops’ in mind when they designed the DC-2 in those early days? Shoe brakes were prone to fade and small town strips not all that long, then. Interestingly my USAF C-47 flight manual mentions ground loops as a backup manoeuvre to stopping, when all else fails, but gives no details!
Those of you who had early experience of the 'Gooney Bird' in WW11 may be able to answer this question. ?
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