Not Enough Dual

Boys in Tiger Moths

The Chief Flying Instructor in the front cockpit grabbed his end of the Gosport tube and shouted “You’re using far too much rudder!” into his rubber funnel. I glanced at my Slip and Skid needle, top of the largest instrument on the panel. He was correct, it pointed to the right, too much left rudder, though I think far too much was a bit over the top; but he was not wrong. I corrected this and simultaneously understood what I already understood but had temporarily forgotten while making the gliding left turn on to our final approach.

At this point in the 30 hour course I had nearly 5 hours of dual experience - almost a whopping 300 minutes of concentrated learning for a 17 year old. This was my first flight with the CFI and it continued without further interjection, but his reaction to this brief lapse of technique was a salutary lesson in priorities and the importance of paying attention to the rules when in charge of an aeroplane’s controls, whatever your excuses. This subject was never discussed because this was an excellent school. Satisfactory teaching was taken for granted, and he trusted his staff. During the next detail with my usual instructor, the only other one, I was sent solo. The same afternoon this instructor said “I’ve got some more solo for you,” and briefed me on the lawn mower. I duly cut the grass in front of the clubhouse, but I can tell that he was pleased with his achievement. He was not normally given to any hint of humour with students, and I cannot claim all the credit for my progress.

The Tiger Moth rudder control circuit is biased to the left by a spring, permanently set to trim the required rudder position for straight cruising flight. More propeller influence, when climbing for example, requires more left rudder, therefore some left foot push. Gliding flight requires a central rudder position, calling for an element of right foot load just to hold the rudder straight against its spring. A gliding left turn calls for some left rudder, but whether relaxed feet might give you just the position you require depends on other variables. An instinctive and logical left foot push for left turn, right for right works for a glider, but engines and propellers require an additional specialisation — educated feet.

It wasn’t as if I had got into a dangerous situation, but sideslipping (or its skidding reflection) had gone out of fashion as an acceptable mode of normal flight many years before. We students had already learned deliberate sideslipping as a means of steepening the Tiger Moth approach, but deliberate is not the same as an oversight. Balanced flight had long become an important requisite for normal single engined flying. Unintended sideways motion brings the spin closer, especially when making a turn on to a final approach.

How it used to be

The very early days of powered flight demonstrated some different ideas about how to turn. The flat turn (while skidding to the outside) was popular to begin with for two reasons. If you banked you might fall out over the side, or the flying machine might fall out of the sky because the lift of the wings was not aimed directly upwards. In addition, a flying device that could not climb out of ground effect did not have enough ground clearance for risky banking anyway. The Wright Brothers knew better, they ran a bike shop, understood the dynamics of turning motion, and during their 1908 European tour banished this folklore for ever — almost. Their large two seat Wright Flyer took all and sundry for rides, their elegant banked turns demonstrated the efficiency and safety of balanced flight, and no one fell out over the side. The hitherto confident French looked on and agreed, ‘The Brothers are the masters of flight.’

Strange but popular folklore

The previous paragraph includes the word ‘almost’ because you can still come across strange ideas in unlikely places, suggesting that elements of folklore can persist, and be accepted as mysterious truth. Fifteen years after the end of WW2 my father, once an experienced bomber pilot and Operational Training Unit instructor, told me a remarkable thing. ‘In a steep turn the rudder becomes the elevator and the elevator the rudder.’ This statement has a certain elementary logic to an inexperienced beginner, and sort of applies to slow roll technique if one forgives the semantics, but it fails to understand the fundamental physics of turning flight. I can’t imagine that he employed the technique in his Mosquito, or even the Hampden. But was this a piece of apocryphal folklore that had circumvented the Central Flying School and spread in OTU circles? I cannot believe that such ideas were still put about by qualified instructors of beginners, but OTU life reminds one of airline training of days gone by. ‘You’ve got your wings, this is just another aeroplane, get on with it. If you get it wrong you can try again (if you’re lucky, or still alive)’.

The Hampden was a single pilot aircraft, no dual controls. By all accounts its handling was liked by its successful pilots. Its students will have already become twin engine qualified on the Oxford, and the Upper Heyford training organisation also used the dual control Anson for some training functions, but the bigger and more complicated Hampden was a step up, for sure. If an instructor, valued for his operational experience, was not to be put at unnecessary risk the system for releasing a student to fly the Hampden was obvious. This applies to many single pilot, twin engine craft. The instructor flies first, demonstrating the basics, and the student stands behind, trying to remember all he has heard and seen. Then they change positions. The instructor observes the preparations up to the before takeoff checks, gives a reassuring tap on the student’s shoulder, says off you go and leaves the aircraft.

Not very confidence-inspiring, one might think, but the risk of a real engine failure (or a mistake) on this first takeoff at the controls does not warrant the loss of an experienced advisor who has no means of physically intervening: this requires real dual controls. At this stage in the story the reader should understand that times were pressing in 1942, and the object of the whole training sequence was to produce potential commanders of four-engined bombers in the minimum time possible — each with the confidence, however fragile, to actually pull off a first mission. There are times when how-do-you-feel hand-holding has to cease.

Problems of Adjustment

Training is traditionally managed and delivered by people of some experience. This sounds like good sense, but there’s often a problem here. Can the staff put themselves into the mind of a learner? They were learners themselves once, but the ability to mentally rerun the process in detail requires a special kind of memory, and a certain element of self-obsession and analysis of minor detail. With each day of learning progress, assuming success, the typical memory wipes much of this tape, leaving it fresh for the next day’s challenge. By the end of a very memorable tour of bombing operations, the detailed memory of how, as the only pilot in the aircraft, this once novice had managed his first OTU takeoffs and night circuits has been successively wiped by much more recent and attention-getting experience. Good teaching can benefit from personal experience, but only if this experience has been distilled and saved in the teacher’s memory, and recalled when transferring the important but forgettable details of this building process. There were plenty of accidents at No.16 OTU. Loss of directional control on takeoff was common.

The solo-only, single fin Rapide, with a mere 200HP a side, definitely requires right engine lead for the initial takeoff run. Note the different fixed-pitch propeller appearances here.

A takeoff in a multi engined tail dragger frequently requires carefully judged asymmetric opening of the throttles, and the Hampden, even with its two fins and rudders, was no exception. The ability to apply full rudder, as a limit to how much power you can apply as the takeoff progresses, is helpful, and a member of 16 OTU staff investigated the reasons for the frequent takeoff prangs. His report concluded that all pilots must make sure the rudder pedals are correctly adjusted to suit themselves, before start up. It seems that, like the TIger Moth and other training aircraft, this was frequently not done, if at all. I do not remember this facility ever mentioned during my three years of Tiger Moth and Chipmunk flying, both of which had a set of three holes and a securing pin for each rudder pedal. Old, well-used Tiger Moths showed little evidence of these pins ever having been moved since the machine left the factory, and I was never aware of anyone else making the head first descent to the dark cockpit floor to make this inconvenient adjustment. The vast majority of students managed with the aircraft as left by the previous occupant. The 16 OTU Squadron Leader also recommended that ground crew should leave Hampden rudder pedals fully aft at the end of each preflight check so that the next pilot had to set them for himself. Perhaps this was easy to do - like the Concorde’s beautifully crafted adjustment for the feet. One notch forward of fully aft suited me perfectly.

Stabilised Yaw

Has anyone heard of this phenomenon applied to other types? In his ‘Flights into History’ author Ian McLachlan states:

The ‘stabilised yaw’ was a notorious feature of the Hampden that derived from a design flaw. If the controls were not smoothly coordinated in a turn, the aircraft would side-slip. In some situations the forward fuselage then blocked airflow over the rudders, rendering them ineffective. Given adequate height (and sometimes the use of throttles) a pilot could recover but at low altitude there was never enough time to retrieve the situation. Pilots were also warned to avoid flat turns, for the same reason. Despite the aircraft’s reputation, David Penman was comfortable in his cockpit:

‘It was a single pilot aircraft and no dual could be given. To me it was a delightful aircraft to fly, though others might not agree. It had a large roomy cockpit, which offered an excellent view, the controls were light and responsive, and with large flaps and also leading edge slots it handled well at low speeds. However, it could swing badly at takeoff, had a very poor single-engine performance and could get into a stabilised yaw which caused many accidents . . .’

Pilot Officer David Penman was a little ahead of the game in aircraft handling experience, having enlisted in 1937, and was better placed than the many who followed during the desperate catch-up days and nights of the early 1940s. Following the Tiger Moth basics he flew the Audax and Hart, two of the Hawker biplane, open cockpit light bombers, then moved to the Bristol Blenheim, one year before the outbreak of war. Of the arrival of the 44 Squadron Hampdens he says ‘We were glad to receive the first of our Hampdens in February 1939. The Hampden, though not quite as fast as the Blenheim, was a much better aircraft all round.’

As soon as hostilities started, the relatively defenceless daytime nature of this generation of aircraft when attacked by a party of Me.109s flown by well-trained aerobatic Germans became obvious, and day bombing turned to unfamiliar night. Much had to be learned. Penman comments on the good supply of Hampdens, but a shortage of crews. ‘The very high accident rate at the Hampden Operational Training Unit did not help. For pilots just out of training school with little more than 150 hours on Tiger Moth and Oxford, it would not have been easy.’

Bearing in mind this short-track, no dual, night as soon as possible training requirement, is it fair to blame some of the accidents on a design flaw? A revealing comment which follows the mention of uncoordinated turns (unbalanced due to incorrect pilot rudder position) is the warning that pilots should not perform flat turns. This advice suggests that such a method of turning, presumably deliberate, might have indeed been part of the folklore amongst OTU discussion. My father’s comment mentioned in the previous folklore paragraph strongly suggests the idea of inappropriate technique, and helpful amateur advice can spread like wildfire among concerned students — especially in a solo only school. And did the solo students actually practise their engine failures and single-engine approaches at night by themselves? Wow!

If you add the two disquieting features above — slipping and skidding turns, and single-engined circuits at night — we can understand P/O Penman’s observed ‘very high accident rate’, and dashing BOAC B707 training captain Jimmy Linton’s comment about the action at Upper Heyford in 1942: ‘You could tell where the circuit was at night because of the fires.’ Was this a popular joke, or real? I don’t know. A grain of truth, perhaps.

Was the problem really the Hampden’s funky shape?

An authoritative description of this aircraft’s actual stabilised yaw behaviour may be recorded somewhere, but I have not come across it. What did it actually do? The word ‘spin’ sometimes features in reports, but this word is frequently bandied about in connection with anything that goes round and down, with little regard to science. The vertically pronounced and narrow forward fuselage may well have produced significant vortex shedding when presented to the airflow at a modest sideslip angle, thus rendering the downstream fin and rudder ineffective. Looking at the drawing, ten degrees might be a generous guess.

And the considerable lateral fuselage area ahead of the centre of gravity — somewhere between the aerial mast and the directional loop — might provide a considerable destabilising influence when only one fin/rudder surface remaining to resist it. Did the Hampden just go waltzing sideways and round, of its own accord, while still flying rather than — or before — actually spinning? A pilot’s initial instinctive nose up response to the Hampden’s natural attempt to descend and maintain its speed in response to the increased drag would not help at circuit height. The immediacy of correct restorative action would have been vital.

Keep the wind in your face

This advice is even more important than ball in the middle, even considering the more sensitive slip/skip needle of olden days. Top Gun enthusiasts will remember the time when Maverick’s Tomcat flew through someone’s jet efflux and one of his two engines flamed out. During the resulting asymmetric mayhem (throttles wide) he got into a flat spin, from which he could not recover. This episode is based on a true feature of this aeroplane. The result is a short piece of soft nylon rope secured at the bottom of the windscreen. It’s there all the time. ’Keep the string pointing towards you, boy.’ Who needs dual? Just remember no flat turns, or top rudder to raise the nose.

Would a dual control Hampden trainer have helped?

Unquestionably yes, but that was then. What do the pinning on of wings, or issue of a licence actually mean? Life is an endless learning process. Flying is no different, and no two students are exactly alike, even if the challenges are the same. An arbitrary required standard is a convenient milepost in a long journey, but a stamp and a signature do not guarantee a trouble-free future. It takes imagination, real experience, empathy and memory to enable an instructor to analyse the potential difficulties of the new challenges that confront a student in a new environment, at any level, regardless of paper qualifications — on both sides. The right corrective advice, having correctly identified the problem, can have instant and very economical effects: problem solved.

It is clear that the great majority of solo-only Hampden students came to terms with this wide step from the Oxford, and went on to complete operational tours on Lancaster, Halifax et al. We should also not forget the immense pressure faced by government and the bombing industry to make up for a historical determination not to wage war again. This is certainly a nice idea, but time was pressing, and the alternative was eventually considered unacceptable by the imaginative section of the enlightened world.

Do we face a similar human situation today? Certainly yes, and on a big scale: but what has this to do with how much dual flying training? The better the quality of the dual the less you need, and the sooner the fledglings fly free and safe. This applies to all elements of growing up and facing reality as we know it.