Flight Test: Beech 18 Expeditor
PUBLISHED: 10:49 09 March 2017 | UPDATED: 10:50 09 March 2017
Flying this iconic aircraft is a challenge, in terms of preparation, operation and landing — but what a joy!
There are few things more sonically satisfying than operating the twin throttles of a pair of well-tuned radials. As we rumble across the Berkshire countryside owner Tim Darrah gives the port prop lever the tiniest of tweaks and then they’re beautifully synched. I glance at Tim and we both grin at each other. No words are necessary – the grins are enough. Sometimes, life’s a Beech!
Known variously as the Model 18, Twin Beech, C-45 and Expeditor, this iconic aircraft has long been on my ‘wish list’, so when the opportunity arose to fly one I hesitated for only a fraction of a second.
The prototype made its maiden flight from Beechcraft’s Wichita, Kansas plant on 15 January 1937, and over the following 32 years it remained in continuous production, around 9,000 being built. During that time over 200 modifications were incorporated, including fitting a tricycle undercarriage and turboprop engines. The subject of this flight test, G-BKGL was built during WWII and then re-manufactured as a D model for the RCAF in 1951.
As Tim and I wander out on a beautiful autumn day at White Waltham, my initial impression is that it is quite a big aeroplane, while the US Army Air Force paint scheme gives it a wilful, almost aggressive appearance.
The first task is to pull each engine through nine blades (to avoid hydraulic lock) and then Tim shows me around. As we’re already standing by the engines, he tells me that power is provided by a pair of Pratt & Whitney R-985-AN14B supercharged nine-cylinder air-cooled Wasp Junior radial engines, which produce 450hp each at 36in manifold pressure and 2,300rpm, and turn Hamilton-Standard Hydromatic metal two-blade constant-speed propellers. Each engine has its own independent fuel system consisting of two tanks in the relevant wing, plus an auxiliary tank in the nose.
Unusually, the air intakes are mounted inside the cowlings, while the intakes for the oil coolers are recessed in the wing’s leading edge, just outboard of the engines. The wings are built in three sections: the centre section is integral with the fuselage and carries the engines and main undercarriage. It features a single steel tube monospar which is joined at mid-span to duralumin girders. Each wing has large metal-skinned plain flaps which are actuated electrically, the cowl flaps use cables. Access to the cabin (which can carry up to eleven people) is via a door on the port side, just aft of the wing.
The very big tailplane (although relatively short-coupled the Expeditor has a broad C of G range) carries a huge elevator, twin fins and rudders. With the exception of the flaps, all the flying control surfaces and their associated trim tabs (the elevator has two) are fabric-covered. The main wheels are fitted with big hydraulic disc brakes and use an electric motor to retract aft into the engine nacelles. When retracted, doors cover the undercarriage legs, but about half of each wheel still protrudes. The castoring tailwheel can, and must, be locked for takeoff.
One thing’s for sure, with a maximum all-up weight of almost four tons, a wingspan of 14.5m and two 450hp engines the Expeditor definitely qualifies as a ‘big taildragger’. Consequently, before even thinking about starting the engines,
I sat in the cockpit with Tim for some time, familiarising myself with the controls.
Aircraft of this vintage are usually ergonomic nightmares, and the Expeditor is no exception. There are buttons, knobs, levers, handles and switches everywhere−even under the seats! Just to confuse things further, both the layout of the primary flying instruments and the power control levers are completely non-standard.
Although often operated as a ‘two crew’ cockpit, as with most machines of this era the panel isn’t duplicated left and right. Instead the flight instruments are on the port side, and the paired engine gauges are grouped in a central column, three deep. Each gauge has multiple pointers and shows rpm, manifold pressure, oil and fuel pressure, and oil, carburettor and cylinder head temperatures. I found the engine instruments relatively easy to interpret, but the flight instruments... Forget it! As with most American aircraft of the 1940s their layout is completely non-standard and difficult to scan.
Oddly, there’s another carb heat gauge by the ASI, while the ammeter, voltmeter and fuel gauge are half-hidden behind the pilot’s yoke.
The fuel system is worthy of further comment as there’s only one gauge, even though there are five tanks (two in each wing and one in the nose). There’s scope for real confusion here as, when you select a tank, the quantity remaining in that tank is shown on the gauge in tenths. However, the front tanks are larger than the rear, so although the gauge may show that, say the front port is 4/10ths full and the rear port 8/10ths, there’s actually more fuel in the front tank.
A centre console carries the power levers in a non-standard arrangement, with the prop levers nearest the pilot, mixtures nearest the co-pilot and throttles in the middle, along with levers that control each engine’s manifold heaters and oil shutters, and flap and undercarriage selectors.
A flat sub-panel below the console carries the fuel valves, T-handles for the tailwheel lock and park brake, plungers for oil bypass and oil shut-off, engine primer and fire suppression selectors. Two handles next to the pilot’s right knee, which resemble handbrakes from a vintage car, operate the cowl flaps, while a large red lever by the co-pilot’s left hip works the wobble pump.
A big wheel on the right side of the pilot’s seat operates the elevator trim; there’s a small wheel for aileron trim between the flap and undercarriage selectors and a handle in the roof (which resembles a car’s window winder) for rudder trim. Elevator, rudder and flap position indicators are above the columns of engine gauges, directly below the two large, red guarded ‘prop feather’ buttons. Finally, a red handle (which resembles a truck’s window winder) in front of the elevator trim wheel is used to manually operate both the undercarriage and the flaps.
Just like the exterior, everything is built to last. The yoke is suspended from an arm that looks like it’s been borrowed from a bridge, while the rudder pedals are clearly designed for pilots who wear boots.
Finally, we get down to the business of starting this big, twin-engine warbird. As has probably become apparent, starting it is very much a ritual, with a considerable number of buttons, switches, knobs and levers to be pushed, pulled, twisted, turned and set. Items that pilots of modern aeroplanes will be unfamiliar with include pushing in the oil shut-off plungers, opening the cowl flaps, closing the oil shutters and selecting the fire extinguisher to the appropriate nacelle. Tim starts ‘his’ motor with barely a murmur−and now it’s my turn, so I crack the throttle open slightly, shout “clear prop” and energise the starter.
Slowly, the big two-blade propeller begins to revolve and after six blades scythe past the window I turn on both magnetos. From within the bowels of the cowl comes a cough and a grunt as a couple of cylinders fire somewhat hesitantly−then a backfire. Argh! A few more cylinders fire and the motor begins to wake up. Smoke streams back from the exhaust and suddenly the remaining cylinders burst into life, turning the two propeller blades into a single shimmering circle and the engine soon settles into that wonderfully liquid radial rumble. I’m not really an animist, but sometimes I swear that these big old engines actually do ‘come to life’.
While the motors warm up, I notice several people standing by the fence and give them a cheery wave. Clearly the sound of a pair of Wasp Juniors grumbling away has generated some excitement, and not just in me. I’ve been lucky enough to fly several truly iconic aircraft over the years and, although it’s easy to become blasé, I’m genuinely looking forward to trying to tame this charismatic machine. However, my excitement is tinged with trepidation, as−particularly when taking off and landing−the Expeditor does have a reputation for being a bit of a handful, if not a real, 24-carat SOB (and I don’t mean “son of a Beech”!)
As soon as the oil temperatures reach 20°C and the cylinder head temperatures are above 100°C (and no, I don’t know why the instruments of an American aircraft built 64 years ago are in centigrade) Tim eases us out of our parking spot and gives me control. Steering is by a combination of differential thrust and differential braking, so as soon as we’re rolling I draw the throttles back immediately and carefully set exactly 800rpm on each engine. This is important, as even a suggestion of differential thrust will make taxying more difficult. The field of view isn’t bad, but I’m still glad Tim is keeping an eye on his side.
The pre-takeoff checks are quite comprehensive and include cycling the props and testing the feathering system, ensuring that the oil shutters are set and the oil bypass in, fuel selectors to front and crossfeed off. All the trimmers are set to neutral, with the flaps lowered to 15° and the cowl flaps set to ‘trail’. Last, but by no means least, the tailwheel must be locked once you’ve lined up.
Tim has around 25,000 hours total time (including about 1,000 in DC-3s) and the takeoff brief is both succinct and comprehensive, and includes the procedures to be adopted in the event of an engine failure both before and after ‘blue line’ speed (the Vyse of 80kt) has been attained. We also review the other critical air speeds, such as the limiting speeds for the undercarriage and flaps and confirm that a good climb-out speed will be around 100-110kt.
Having lined up carefully with the centreline and ensured that the tailwheel is locked; I take a deep breath then smoothly and gently open the engines up to 36 inches of manifold pressure and 2,300rpm, leading slightly with the port engine to counter any tendency to swing.
The engines’ rumble swells to a roar, the rudders come alive almost immediately (a benefit of the twin-tail design as the rudders are in the propwash) and the needle of the ASI starts to move. I feel the throttle levers move slightly under my hand as Tim fine-tunes the power, and concentrate on keeping straight. As the airspeed continues to build I gingerly ease the yoke forward. With radial engines swinging big props there’s a great mass of metal whirling around on each wing, and gyroscopic precession is a force to be reckoned with. Pick the tail up too quickly and a swing is almost inevitable.
As the mighty motors roar out their one-note song, the Expeditor accelerates... expeditiously. With 900 horses pulling eagerly the speed is surging towards eighty and I can feel the wheels starting to skip as the wing takes the weight. I ease the yoke back gently; the skipping stops and we’re off the ground! I check forward on the yoke slightly to stop the nose rising, as we need to accelerate quickly past ‘blue line’ speed.
“Positive rate,” says Tim. “Gear up,” I reply and he selects undercarriage up. As the main wheel legs retract backwards there’s a very subtle nose-up change in pitch trim which is easily trimmed out, and we climb away with the flaps up, undercarriage retracting and the speed well past ‘blue line’ and still increasing. At 500ft I pull the throttles and props back to the max continuous settings of 33in/MP and 2,200rpm, promptly followed by a further reduction to climb power (28/2,000), and set off in pursuit of the Nanchang carrying photographer Keith and pilot Lawrence.
Typical cruise power at say 8,000ft is 27/18, and even at this relatively low setting the engines are still guzzling gas at a wallet-draining 160 lit/hr!
Moving into formation for the photos is a bit tricky, and I’m constantly jockeying the throttles, including setting the thrust up quite asymmetrically to help me hold the right position for Keith to obtain a head-on shot. Our vintage motors probably don’t care for this sort of treatment, and out of the corner of my eye I see Tim tweaking a cowl flap here, an oil shutter there or just adding a bit of manifold heat. We soon get the pictures in the can and, after a final spirited break (see p.30 − Ed), we part company with the Nanchang and I can begin to evaluate the aircraft more thoroughly.
An examination of the general handling soon reveals that, although the controls are reasonably heavy, they are quite effective, and even relatively steep 360° turns aren’t difficult, as the controls are nicely harmonised and the control authority good.
Unsurprisingly the Expeditor has positive stability around all three axes, and I think it would not be too onerous to fly on instruments, as long as it was trimmed correctly. That said, scanning the non-standard panel probably isn’t easy.
Talking of trim, the only trimmer I adjusted was for the elevators, and even then probably less than one turn of the big wheel (it is very powerful). The visibility is pretty well what you would expect of a WWII transport−not bad, but not brilliant.
For a look at the engine-out characteristics Tim set the power so that I effectively had zero-thrust (i.e. replicating an engine that was shut down with the prop feathered).
The performance was perfectly acceptable, but that observation must be qualified by pointing out that we were a long way below MAUW. Losing an engine just after takeoff on a hot day with a full load would be seat-chompingly worrying, particularly if you’d taken off towards high ground.
Slow flight is surprisingly benign, and with the flaps down and a bit of power I actually get the ASI’s needle flickering just below seventy, while Vne is 220kt.
All too soon it was time to return to base and, as we cruised back towards White Waltham in a gentle descent with the engines just loafing along, it was easy to imagine what it would’ve been like flying this aircraft over the Canadian Rockies, half a century ago.
As with the other big piston-powered aeroplanes that I’ve flown, it’s a lot more than the sum of its parts, which are really simply a disparate collection of metal, rubber and plastic. I know it’s a cliché (which I’m aware should be avoided like the plague) but it’s irrefutable: this thing’s got soul!
Having joined overhead, we wait until we’re downwind and then get busy with the flaps, cowl flaps and undercarriage before I sit up a little straighter in my seat. Now comes the real challenge; landing. As mentioned earlier, the Expeditor does have a reputation, and I know it has humbled many a better pilot than me.
There’s a very slight nose-down change in trim as the wheels lock into place, but it’s very subtle. Having levelled off at 800ft I reduce speed to 100kt and turn on to base leg. I can feel myself tensing up on the controls so momentarily relinquish my grip on the yoke and then hold it somewhat more loosely.
I’m really concentrating and am very conscious of being entrusted with a rare piece of aviation heritage. The thing about big taildraggers is that, unlike a nosewheel aircraft, they’re inherently unstable on the ground. We both know that if I cock it up, Tim will have his work cut out rectifying things−if, indeed, things can be rectified. If a real swing develops, we’ll just be along for the ride. However, although a swing is always lurking for any taildragger, the twin fins and powerful rudders make the Expeditor quite controllable directionally.
The big issue for a Twin Beech, and especially at White Waltham, is the bounce. If it starts to pitch and heave on the mains I’ve got to pin it, or go around. Otherwise a pilot induced oscillation is almost inevitable.
As I bank on to final, Tim lowers the rest of the flap and I draw the throttles back slightly, lower the nose and push the prop levers all the way forward. Everything’s looking good. The speed, angle and sink rate are all bang on, and luckily for me the 1,100 metres of Runway 25 are slap into about twelve knots of wind. (In fact, luck has nothing to do with it. The truth is I’ve been waiting weeks for today’s conditions, and have cancelled two previous opportunities. I didn’t fancy either of the other, shorter runways, and as for a crosswind, forget it; the demonstrated 90° crosswind component is only 11kt.)
As we slide down the slope with the speed slipping back towards the Vref (aka ‘over-the-hedge’) speed of eighty, I feel my confidence build. Good landings come from good approaches, and this is a good approach. As we sail over the hedge at exactly eighty I squeeze the throttles closed, check the sink rate and then let the aeroplane settle gently on to the main wheels. The actual touchdown is gratifyingly soft, but after a short roll we hit one of White Waltham’s notorious bumps and skip slightly, before settling again. I push lightly on the yoke to pin the mains on, and then sense Tim adding just a little bit more push, to get the weight firmly on the wheels.
We’re down and rolling out nice and straight, but we’re not stopped yet and−wary of precession−I gently fly the tail down on to the ground. I’ve done it, but even at the end I nearly blot my copybook, by starting to turn off the runway faster than a walking pace.
“Steady,” Tim cautions, and I quickly straighten up and come to a stop, then unlock the tailwheel and taxi clear of the runway. Flaps up, cowl flaps open and I turn to Tim with an enquiring “Well?” “You know,” he replies in his soft Irish brogue, “I doubt you’ll get a much better landing than that on this runway”. “In that case,” I laugh, “let’s quit while we’re still ahead!” A bit of me desperately wants to do another couple of circuits to see if I can make a better landing, but my pragmatic side knows that this is unlikely.
Back at our parking spot those marvellous motors continue to pulse through the airframe with their deep, rhythmic throb and, with the shut-down checks complete, I reluctantly draw the mixture levers back into ‘Idle/Cut-Off’, the engines die away and the propellers slowly windmill to a stop.
Tim quickly unstraps and goes aft to open the door but I’m in no rush, so just sit back, slide my window open and enjoy the peace and quiet of simply doing nothing. With a start I realise that the back of my T-shirt is damp. I must’ve been really concentrating−and I had Tim to hold my hand. This is quite a demanding aircraft to operate, especially single pilot. After another couple of hours of Tim’s excellent training I could probably fly it solo, but VFR on a beautiful autumn afternoon over England’s leafy shires is one thing, hard IFR on a dark and stormy night over the Rockies would be quite another!
As I climb out Keith wanders over and grins. “That looked OK,” he offers, and I grin gratefully. Tim and Lawrence appear from behind the twin tailplane smiling broadly and I smile back. Suddenly, we’re all grinning inanely at each other.
What can I say? It’s been a good day at the Beech.
BEECHCRAFT D-18 EXPEDITOR DIMENSIONS:
WING SPAN: 14.5m
WING AREA: 32.4sq m
WEIGHTS AND LOADINGS:
EMPTY WEIGHT: 2,620kg
MAX AUW: 3,980kg
USEFUL LOAD: 1,360kg
WING LOADING: 122.4kg/sq m
POWER LOADING: 5.99kg/kW
FUEL CAPACITY: 1,068 lit
CLIMB RATE: 1,190fpm
SERVICE CEILING: 20,500ft
2 x Pratt & Whitney R-985-APS4 Wasp Junior supercharged nine-cylinder air-cooled radials, producing 450hp (336kW) each at 36in MP and 2,300rpm, turning Hamilton-Standard ‘Hydromatic’ metal two-blade constant-speed propellers
MANUFACTURER: Beechcraft Wichita, Kansas