Tomahawk

The important thing to remember is that you should not use the ‘standard’ spin recovery in a Tomahawk. Think about it for a moment…

I first flew one three decades ago, when the type was new. Having learned to fly on stately Cherokees, I immediately warmed to this precocious sibling. Today, the Tomahawk is far from new, unlike its spiritual successor which we flew last issue, the Whitney Boomerang.

But, while perhaps not pretty, the perky Tomahawk is nevertheless far from unattractive.

Nose-low and tail-high, our test aircraft G-BTJL made a nice contrast to the humdrum Cessnas scattered around it, while our photo subject, fellow AA contributor Owen Zupp’s immaculate VH-PAA, shows how good the Tomahawk can still look.

The Tomahawk’s neat and pleasant lines have survived the test of time. Its tadpole body incorporates a decent sized cockpit with two doors and plenty of glazing, giving the all-round visibility so essential in a busy training circuit.

Long, slim wings suggest fair field performance and a good climb, while the parallel chord predicts only a moderate roll rate. The thennew NASA GA(W)-1 aerofoil is an unusual 17 per cent thick. This was renowned aerodynamicist Dr Richard Whitcomb’s – hence the (W) – first attempt to devise a ‘laminar flow’ airfoil for general aviation use (the GA bit of its designation). Early computer studies predicted a combination of good lift at low speeds, minimal cruise drag and predictable stall qualities.

Regrettably, as is so often the case, this wing section turned out not to be quite so good as he hoped, partly due to surface contamination and inflight distortion of the thin wing skins, and to some extent because of Piper’s reputation for poor quality control on the Tomahawk production line. This aerofoil was also used on the Beech Skipper and a handful of lesserknown designs such as the British Edgley Optica before fading into obscurity.

Unusually, all Tomahawks have slim, wedge shaped stall breaker strips on their outboard leading edges, ahead of the ailerons. By now, most also have another pair inboard. These make their stalling behaviour more predictable, but do increase stall speeds by a couple of knots. Some wrinkling was evident in this example’s fairly thin wing skins. This could partly account for the type’s reputation of having an unpredictable stall. The reasonably sized, fluted ailerons are plain, with piano hinges, limited deflection and only a small differential, suggesting some adverse yaw would be present – a very good thing in a trainer. The similarly simple, piano hinged flaps have no slots, are quite small, and do not extend right up to the wing roots. This enables the black, non-slip walkways to go right to the trailing edges, but reduces their potential to provide lift and drag.

The Tomahawk’s high set fixed horizontal tail and elevator act as an end plate to its fin and rudder. This enables these to be smaller than would otherwise be necessary with that nicely rounded and tapered rear fuselage, but does lift the horizontal surfaces out of the prop wash. This is good for minimising inflight vibration, and probably helps with spin recovery, but could cause over-sensitivity during rotation on takeoff.

Those simple, spring steel main gear legs have a wide, three metre track and should be robust, but might not be so forgiving as oleos, while the nose leg’s cast torque links and comprehensive support structure were clearly designed with ham-fisted students in mind. The little O-235 engine is set quite well forward, and its neat cowlings are excellent, two over-centre catches on each side allowing a thorough inspection of the engine compartment.

The propeller’s 17cm ground clearance seemed adequate, if not generous.

Piper thoughtfully provided two forward opening doors, each secured by a latch at the rear and a dual catch at the top. This renowned weak point requires careful monitoring to ensure its central hooks properly engage in the doors’ loops. There was also once a flimsy stay on each door, but these are now mostly long gone. Entry is easy, aided by fixed steps behind the wings, those broad walkways and handles above the windows.

The Tomahawk’s cabin is somewhat bigger than a 152’s, and its extensive glazing makes it seem even roomier, although there is a sensible fixed roof area, partly as a strong roll-over protection, but also to give shade from the summer sun.

Most Tomahawk interiors show their age, but it is always nice to see a proper throttle/ mixture quadrant, rather than plunger knobs, while there is safety padding on the yokes. This very sensibly also incorporates the left/right/ off fuel selector (which cannot be turned off without lifting a catch with your other hand) and gauges, at each of which the fuel cock points when its tank is selected. To its right is the primer, while the carburettor heat runs unambiguously in a vertical slot on its left.

The simple black panel might look a little dated, but it is well laid out, in the standard format. The compass and OAT gauge are in the roof, the tacho is immediately left of the throttle quadrant, and subsidiary dials are over to its right. The radios are slightly right of the middle, as usual, with electrical and magneto switches along the bottom on the left, and circuit breakers at the same level on the right.

The short, manual flap lever is between the occupants’ knees. There is no position indicator, their 21 and 34-degree deflections merely being felt as detents. Aft of this is the elevator trim wheel which merely tensions springs in the system. There is no aileron nor rudder trim.

Everything comes to hand nicely, the seats are pretty comfortable, and there are well placed arm rests in the doors.

Some Tomahawks are fitted with proper four-point harnesses, but this one only had the original lap/diagonal inertia reel belts (on which it is vital to check the existence of the shoulder strap locating pin’s plastic sleeve).

Contemporary issues of Jane’s All the World’s Aircraft reveal that the Cessna 152 and PA-38, with effectively identical engines, have quoted cruise speeds, stall speeds and takeoff and landing performance within just one or twoEverything comes to hand nicely, the seats are pretty comfortable, and there are well placed arm rests in the doors. per cent of each other. So, despite its magic new aerofoil, the Tomahawk’s only true edge was its 450nm range – a simple product of larger tanks. Unfortunately its heavier structure means a careful eye must be kept on loading. Indeed, even with somewhat less than full tanks, instructor Martyn and I took Juliet Lima right up to her 757kg maximum takeoff weight. Our 95 litre fuel load equalled a 152’s maximum, but the same flying school’s slightly heavier sistership would have been compromised by 32kg.

I was surprised by the starter, which whizzed our propeller around much faster than usual. Presumably it was a newer, high energy lightweight model.

The parking brake below my panel was easily released, and the nose wheel steering was light and effective. The landing gear is nicely firm and reasonably well damped, although it can develop a cheeky little waddle over very uneven terrain.

Run-up and pre-takeoff checks were completely standard.

However quickly you open the throttle, no Tomahawk will ever surge forward, particularly on soft ground, but she’ll get off in her own time, given one notch of flap, 500m or so and some patience. In reasonable temperatures, on a hard surface, and with anything of a wind she’ll be airborne in under 300. In our case, we had a strong, 20-gusting-30 knot headwind and were operating from fairly long, wet grass, but our run took little more than 200m. Only a touch of right rudder pressure was needed to keep straight, and a positive rotation at 55kt led to a brief acceleration in ground effect to 70 for our climb. Retracting the flaps at 400ft gave no apparent pitch change, and only a small improvement in our climb.

As testimony to the Tomahawk’s willingness, on my previous acquaintance with the type (15 years ago) I had to fly little VH-KTP at maximum weight from Langley Park’s thinly grassed and sandy, 800m temporary airstrip laid out in Perth’s city centre. The wind was nearly calm, giant Canary Island palms loomed 60ft around us, we had a time limitation, and the temperature was 39°C. Knowing the sand’s drag would easily stop us in 200m, I thought it worth one attempt two-up before accepting the inevitable and going solo.

I opened the throttle, the engine wound up to 100 or so rpm below full power (because of the heat) and we trundled soggily forward. Having valiantly accelerated to 30kt, the breathless little thing couldn’t go any faster, for every few metres its nose wheel burrowed into the sand, slowing us down again.

Unfortunately the Tomahawk’s tailplane is above its propeller’s slipstream so, despite holding full up elevator, I couldn’t raise the nose.

Eventually, we hit a lucky tussock, bouncing the tailplane into our propwash and lifting the nose wheel off the ground. Carefully guarding against overcontrolling, I lowered the nose again, to skim the wheel over this sparse grass.

The reduced drag allowed our airspeed to stagger above stall speed, so I hauled the struggling aeroplane off the surface and carefully held it low, in ground effect, until the ASI read 65. I won’t say we soared over those palm trees, but we did clear them by a safe margin, and my admiration for this gallant little aeroplane increased commensurately.

Today, being in formation, I was unable to time our climb, but to my glee, up to 3000ft we lost only a couple of wingspans to the similarly-laden Chipmunk with 33 more horsepower. A tired PA-38 is unlikely quite to manage its quoted 718ft/min climb rate, but most of them should achieve 690ft/min in ISA, generally bettering a 152 of similar vintage.

With our photo sortie complete, at 4500ft I set up a nominal cruise power of 2300rpm, which gave us 93kt IAS (98 TAS) at a consumption of perhaps 23 litres an hour when leaned out. Pitch stability was good, yaw stability was very positive, and roll (spiral) stability was only fair, as you would expect. The Tomahawk has quite good manoeuvrability and surprisingly pleasant controls for an American aeroplane of its day, although the ailerons are rather heavy for my taste.

I timed its roll rate at a reasonable 45 degrees per second, noticing that, at all aileron deflections, it does need some rudder to counter adverse yaw. I think this is absolutely correct for a trainer, and no bad characteristic in any aeroplane.

Visibility is better than from its Cessna rival, despite the rather prominent door pillars, but no longer as good as that exhibited by many more recent European trainers, and that roof does get in the way in turns, particularly to the right. I did not really like the spring bias elevator trim, which I found needed more attention than necessary to get rid of the residual elevator forces, but that is probably merely a matter of taste. Low speed behaviour is an important trainer characteristic. In my opinion an instructor must be able to demonstrate some of the less pleasant character traits that are so often evident in older or uncertified types. Nowadays, many new PPL holders go on to buy homebuilt or kit planes. Most of these have a much less forgiving stall than the PA-28 and Cessna families, so it is important that new pilots have a real understanding that the stall is not to be taken lightly.

In this respect the Tomahawk is good. Slowing for a clean stall, the horn started sounding at around 65kt, and at 56kt there was clear warning buffet, before a positive break at 54. Letting the slip ball wander slightly from the middle of its tube would induce a proper (although limited) wing drop. Half flap did not reduce these numbers by much, and the symptoms stayed similar, but with full flap there was slightly more buffet and again a proper nose nod at 46kt. The POH suggested these figures should be 52 and 49kt for a Tomahawk equipped with both inboard and outboard stall strips.

A practice forced landing verified the Tomahawk’s good glide angle, although this was only slightly steepened by the small flaps. Back on the ground, I thought I could detect interconnecting springs between the rudder and ailerons.

These, combined with the diminutive rudder and rather heavy and not over-effective ailerons made sideslips difficult, and frankly an unproductive drag increasing technique.

Circuit work was easy, aided by that good visibility and the crisp handling.

In moderate turbulence the little dear wiggles its rear end like a 12 year-old in her auntie’s stilettoes, but this can easily be countered by deft taps on the rudder pedals. Approaches at 70kt were easy to control in all axes, and despite the gusty and turbulent conditions it was simple to bracket the speed between 70 and 75 on final. The flare and hold off at this increased speed led to a 200m float (unusual in a Tomahawk) and a proper, nose high gentle landing was easy on those wide, forgiving main gear legs. Our roll out on both occasions was less than 200m in the stiff breeze.

Tomahawk Spinning

Just as Robinson R22 helicopters are legendary for needing cat-like reflexes to establish safe autorotation after engine failure, the Tomahawk has a reputation for unusual spin characteristics. In both cases these myths are largely (although not entirely) unjustified.

The important thing to remember is that you should not use the ‘standard’ spin recovery in a Tomahawk. Think about it for a moment… This standard spin recovery, as taught by most flying schools, requires a pause between applying full rudder and easing the control column forward. But do you know why? Because, for most aeroplanes, when the elevator is fully down, much (indeed often almost all) of the rudder is blanked by the tailplane and elevator from the local airflow which, in a spin, will be at an angle of attack of perhaps 20 degrees. That pause with the stick back allows the biggest possible rudder area to have the maximum effect in opposing your yaw before you try reducing the angle of attack.

The Tomahawk’s tailplane is above its rudder, so the rudder has maximum effect from the word ‘go’. Delaying moving the yoke forward merely invites the aeroplane to enter a faster secondary spin mode (although it will sometimes merely recover after 1½ further turns). So, the correct Tomahawk recovery is: check the throttle is closed and the ailerons are central, apply full opposite rudder, and the moment the rudder hits its stop, push the yoke forward. Unfortunately, since this technique differs from that used in most other aeroplanes, it seriously reduces the Tomahawk’s effectiveness as a trainer.

Additionally, in the words of the UK CAA’s light aircraft test pilot of the time it needs a “firm push to unstall” and, occasionally is “recovered in a ¾ turn with a sick-making bunt”.

As always, you must then centralise the rudder the moment the rotation stops (or you risk transitioning into a spin the other way) and promptly but gently ease out of the ensuing dive.

So its tai l wobbles?

Of course it does. All tails wobble, especially in a stall or spin. This is caused by that warning elevator and tailplane buffet you feel through the controls.

The difference with a Tomahawk is that you can look over your shoulder and see it happening.

Airframes have to bend. Building them rigid would make them prohibitively heavy, while their very flexibilityhelps them safely shrug off excessive loads.

Next time you fly through turbulence in an A340 or 747 (or even an old DC-3 Dakota), watch the wings. They are flexing not only to shed undue stresses, but also to absorb those gusts and give you a smoother ride, just like the invisible (but similarly elastic) suspension on your car.

When I was learning to fly Boeing 707s, my more fortunate buddies were training on the VC10, a British jetliner renowned for, among other things, the rigidity and mass of its structure.

While their colleagues practised stalling, these trainees were encouraged to peer through the navigator’s roof-mounted periscopic sextant at their aeroplane’s tail. Sure enough, despite their airframe’s supposed inflexibility, the whole rear end quivered and shook, just like a Tomahawk’s.

Minovation’s KTP

Western Australian flying training school Minovation is still operating the oldest PA-38 in Australia and the second oldest flying Tomahawk in the world. VH-KTP was one of the really good early examples. Indeed it is construction number 38-78A 0006, making it only the sixth built. Imported as the demonstration airframe, it was registered KTP as Keith’s Tiny Piper.

KTP started its proper training life with Trevor and Eunice Baxter’s Jandakot based Amity Aviation (which was how I came to be flying her out of Langley Park) before passing to Minovation as Karls’ Tiny Piper. Having amassed over 11,000 flying hours, she is enjoying a new lease on life with the wing life extension kit – four spar root doubler plates which give her 7000 more hours.

Soldiering On

Over the years, a few Tomahawks have been used as low cost, two seat personal runabouts but, since so few (2519) were built over Piper’s all-too-brief, five year production span, they are comparatively rare in this role. Now that more modern, mostly composite trainers have become available, some PA-38s are being sold on by flying schools and refurbished as private aircraft, although I have to say that while the Tomahawk is an excellent trainer, the Cessna 150/152 series probably make better sightseeing aeroplanes.

Prospective PA-38 buyers should be aware there are around 20 ADs and SBs for the type, including a requirement to change the engine mount every 1000 hours. However, Paul Sterling’s wing life extension kit should enable the remaining Tommies to keep going almost indefinitely. See www. sterlingaviationtech. com.

What a shame that Piper stopped building these jaunty little machines in 1982, making even the least elderly example now over 25 years old. The good news is that, as we sampled in the September issue of AA, the Dean Wilson Aviation built Whitney Boomerang is a fitting modern successor, with its low tail and better aerofoil.

But until the Boomerang enters service in numbers, those countless Tomahawks in training schools the world over will just have to soldier on in the job they were designed for, and are so good at: effectively training ab initio students as cheaply as possible, and in reasonable comfort.

PA-38-112
TOMAHAWK

Technical specifications
Powerplant
One normally aspirated,
four-cylinder, horizontally
opposed Lycoming
O-235-L-2C/A, producing
112hp (84kW) at
2600rpm. TBO 2000hrs.
Propeller: 72in (183cm)
diameter, two-bladed,
all-metal, fixed-pitch
Sensenich 72CK-0-56.
Performance
(manufacturer’s quoted)
Sea level Vne 138kt
Max SL speed 109kt
Max cruise (7100ft)
108kt
Economy cruise
(10,000ft) 84kt
Stall, full flap 49kt
SL takeoff dist 445m
SL takeoff run 250m
SL landing dist 447m
SL landing run 191m
Sea level climb rate
718ft/min
Service ceiling 12,000ft
Max range (to empty
tanks) 480nm
Weights & loadings
Equipped empty 537kg
Max takeoff 757kg
Max baggage 45kg
Standard fuel 121 litres
Load factors normal
+3.8/-2g, utility +4.4/-2
Dimensions
Wing span 10.36m
Wing area 11.6m2
Length 7.06m
Height 2.77m
Cockpit length 1.74m
Cockpit width 1.07m
Cockpit height 1.28m