Flight test: SAAB 91D Safir

PUBLISHED: 13:12 19 March 2020 | UPDATED: 13:13 19 March 2020

Saab 91D Safir flight test

Saab 91D Safir flight test

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This jewel of an aircraft effortlessly fulfils its triple design role of trainer, tourer and aerobatic machine – and its easy handling will enchant any pilot | Words: Dave Unwin - Photos: Keith Wilson

As the Safir turns downwind it is starkly silhouetted against the September sky, and for a second the tapered wings, square-cut wingtips and slightly rounded tailplane are reminiscent of the Messerschmitt Bf 109E.

Five minutes later it’s taxying towards me and now more strongly resembles a late model Bf 108, although the heavily-glazed multi-pane canopy also puts me in mind of the Bü 181 Bestmann. This isn’t a coincidence, for the Safir was designed by Anders J Andersson, who had also devised the Bestmann while working for Bücker.

I meet G-XCID and its owner John Hunter on a beautiful September morning at Fenland Aeroclub in Lincolnshire, and it quickly becomes apparent that this is a ‘Mil Spec’ machine that has been built to a specification and not a price.

For example, the typical GA aircraft tail bumper is simply a spring steel strip, but the Safir’s is flexible skid with its own coil spring!

Saab 91D Safir flight testSaab 91D Safir flight test

The rather blunt nose carries a four-cylinder air-cooled Lycoming O-360-A1A, which turns a McCauley two-blade metal, constant-speed prop. Access to the engine is exceptional because the cowling is of the petal type, so the top halves hinge open on both sides and the bottom is hinged at the back.

Replacing the early model’s heavy Gipsy Major with an O-360 meant extending the engine mount to retain the centre of gravity, consequently access to the back of the motor and its accessories is excellent. Also impressive are the deflector plates under the cowling that direct cooling air to the rear cylinders.

A lot of thought went into the engine installation, which makes the curious cowl flaps even more surprising. They can be adjusted, but only on the ground, and as they’re quite big I reckon you’d pick up five knots if you could close them in the cruise.

Other big drag-producers are the large circular landing lights set into the leading edge of each wing (what was Andersson thinking?) and the considerable amount of wash-out.

Saab 91D Safir flight testSaab 91D Safir flight test

The wings are skinned with Alclad forward of the main spar and fabric aft, while the fuselage is a monococque structure with Alclad skinning. Similar Alcad skins cover the cantilever tailplane, fin, ailerons and split flaps.

The latter are quite large, mechanically actuated and have three settings: 0, 17° and 43°. The rudder and elevators are covered with fabric and both feature pilot-controlled trim tabs, plus there’s a ground-adjustable trim tab in both ailerons.

The rugged-looking undercarriage is, unusually, manually operated, with the castoring nosewheel retracting backwards and the mainwheels inwards and into the fuselage, giving a relatively short wheelbase with quite a narrow track.

The nosewheel still partly protrudes when retracted and incorporates a neat little mudguard. Shock absorption is provided by oleo-damped springs on the main undercarriage legs and the mainwheels are fitted with Goodyear hydraulic disc brakes.

Saab 91D Safir flight testSaab 91D Safir flight test

The reason for the undercarriage’s narrow track is because the main undercarriage legs are attached, Messerschmitt-style, to the fuselage not the wings, allowing the wings to be quickly and easily removed.

Each wing is joined to the fuselage by two bolts, one vertical and one horizontal. The electrical wiring and fuel lines are easily disconnected (the fuel lines feature self-sealing couplings) while the wing joint couplings for the flap and aileron control rods are automatic, allowing the wings to be quickly derigged. Ball bearings are used in all the control circuits except in the rudder.

Access to the cockpit is excellent. The wingwalks are wide and there are three upward-opening glazed hatches, one on the port side and two on the starboard. The rear starboard hatch is very large as the starboard seats and control column can be quickly removed to allow the carriage of a stretcher (the rear port seat is retained for a medical attendant).

Alternatively, if all three seats are removed the Safir can carry 250kg of cargo, and even if all the seats are in place there’s a big baggage bay behind the rear seats which can carry almost 20kg and is accessible in flight.

Saab 91D Safir flight testSaab 91D Safir flight test

At almost 1.3m wide the cabin is quite big, and feels bigger due to the copious glazing, and I very much like the large DV panels. Each of the three hatches can be jettisoned by pulling on the appropriate red handle set into the roof.

This (and the fact that the front seats are designed for seat-type parachutes) is because, when flown in the ‘Utility’ category and with a MAUW below 1,050kg, it is aerobatic with load limits of +6/-3g.

The rudder pedals and seats adjust (the seats only vertically), and once strapped in with the very beefy four-point harness I study the cockpit with considerable interest. The slightly curved control columns feel very natural, and as there are two throttles I can fly with either hand.

Between the seats is a big quadrant that carries (from port to starboard) the elevator trim, handbrake-type flap selector and undercarriage lever, with a star wheel for rudder trim at the back. Again, it’s all beautifully engineered. The elevator trimmer can be used for fine adjustment by just moving the lever slightly, while for coarse trim changes the lever is pressed down first.

Saab 91D Safir flight testSaab 91D Safir flight test

To retract the mechanical undercarriage, rotate the oblong top to release the up or down locks, then move the lever ‘forward to fly and back to land’. A red warning light illuminates if the undercarriage is locked up below a certain manifold pressure and there’s a single green for ‘down & locked’.

Although the pattern of the primary flying instruments only loosely follows the Basic Six arrangement, the general cockpit layout is much better than most 1960s light aircraft, the instruments being grouped in three separate sub-panels.

The left one has an ASI, AI, T&S, VSI and altimeter, plus a modern EHSI, while the one on the right side has essentially the same, with a g-meter instead of the EHSI. The central panel has a selection of round dials in two rows.

Saab 91D Safir flight testSaab 91D Safir flight test

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Designed for the military

Anders Andersson began work on the basic Safir design in 1944, with the prototype making its maiden flight in November 1945. This aircraft was powered by a 130hp Gipsy Major IC, but production versions (now known as the SAAB 91A) were all fitted with 145hp Gipsy Major 10s.

It was rapidly appreciated that 145hp still wasn’t enough, and the ‘B’ model used a 190hp Lycoming O-435A. Changing from an inverted inline four to a flat-six required a major redesign from the firewall forward, while for the ‘C’ version SAAB added a fourth seat and changed the fuel system from a single fuselage tank to one in each wing with a combined capacity of 175 litres.

The ultimate variant was the ‘D’. This replaced the O-435 with a four-cylinder 180hp O-360, which, although slightly less powerful than the O-435 was considerably lighter and less thirsty. It also used a McCauley constant-speed propeller with a spinner (earlier iterations used less efficient variable-pitch Hartzell props without spinners) and the net result was a 45kg reduction in the empty weight.

Saab 91D Safir flight testSaab 91D Safir flight test

SAAB eventually built 99 ‘D’s, including the subject of this month’s flight test. Total production of all versions was 323, of which almost a third were built by the Dutch company De Schelde at its Dordrecht factory.

Most were built for the military; the air forces of Austria, Finland, Ethiopia, Norway, Sweden and Tunisia all operated Safirs and the Austrians only phased theirs out in 1992.

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The top row consists of a large tachometer, fuel quantity in each tank and a combined oil temperature/pressure gauge. On the second row are manifold pressure (in Bar), plus carburettor and cylinder head temperatures, with the ammeter and fuel pressure gauge below P2’s flight instruments. The full width panel below carries the parking brake, a row of rugged-looking tumbler switches, starter and magnetos, and−in front of P1−alternate air, the circuit breakers being placed in front of P2.

In the centre are throttle and propeller levers, and there’s another throttle in a sill below the port hatch. The mixture plunger has an unusual spring catch that automatically enrichens the mixture when the throttle is pulled back to commence a descent, while yet another fascinating facet (the Safir is full of them) is that, as there’s no electric fuel pump, you pull vigorously on a T-handle a couple of times to raise the fuel pressure before starting. The rotary fuel selector is right in front of the P1 and works anti-clockwise from ‘off’ through ‘starboard’ to ‘port’.

Saab 91D Safir flight testSaab 91D Safir flight test

Taxying out reveals that the disc brakes are powerful but not ‘grabby’ and the field of view good. As the nosewheel castors, it’s easier if you don’t taxi too slowly−especially when turning.

Pre-takeoff checks complete, I line up with the centreline of Fenland’s 600 metre Runway 36. Ambient conditions are 18°C and 1013hPa, wind from the north-west at between 5-8kt and short, dry grass. With only two POB, not that much baggage and only half fuel, we are about 180kg below MAUW (maximum all-up weight).

Initial acceleration is good but not exceptional and at fifty knots I raise the nose and we lift off at 65, having used about two-thirds of the runway. I’ve chosen to fly right-handed so dab the brakes, swap hands, retract undercarriage and flaps, then go back to flying right-handed.

That undercarriage is very cleverly designed, well-made and perfectly maintained. Although the weight of all three wheels plus the air load is not inconsiderable, it retracts quite easily, helped by a system of springs and bobweights.

Saab 91D Safir flight testSaab 91D Safir flight test

With the undercarriage and flaps stowed the VSI shows a solid 1,000fpm at 75kt and I soon level off, change hands again, adjust power, rpm, mixture, elevator and rudder trim, then put my right hand back on the stick and my left on the throttle. And I’m already really enjoying myself.

Some aircraft take time to ‘dial in’ but as we close on the Fenland Aero Club’s Cessna 172 cameraship carrying Paul and Keith, I swear it feels as if I’ve got at least ten hours on type, not ten minutes. As we coast out near Holbeach I’m feeling very comfortable.

I don’t know if it’s because I’m flying right-handed (which always feels more natural in formation) or that the air above the sea is as smooth as glass, but as Keith’s window pops open and the Safir slides effortlessly into echelon port I just know this is going to be a good shoot.

The Safir has that rarely encountered combination of crisp controls and solid stability. Usually a designer will compromise one aspect for the other, but the Safir was intended for training, touring and aerobatics, and although these quite disparate requirements would tax many a designer, Andersson clearly met the specifications. After all, he’d worked under the great Carl Clemens Bücker, who knew a thing or three about designing light aircraft.

Saab 91D Safir flight testSaab 91D Safir flight test

Manoeuvring less than a wingspan away from another aircraft will always show up any design deficiencies and the Safir just feels ‘right’. The ailerons have authority, the elevator is powerful and the rudder well weighted.

Control harmony is perfect, and the lasting impression is of a well-balanced, nicely harmonised machine with pleasantly light controls which provide powerful, precise handling along with negligible ‘stiction’ and low breakout forces. All those ball-bearings in the control circuits really do make a difference.

The field of view is excellent, as the multi-pane windscreen is large. You’d think the heavy framing might be intrusive in close formation but it’s really not; I barely notice it at all. Indeed, this is one of the easiest shoots I’ve done in a while. Keith soon calls “it’s a wrap!” and I break down and away from the 172 in a long graceful arc and head back towards the coast.

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Sweden’s own

SAAB is an acronym of Svenska Aeroplan AB, which is Swedish for the imaginatively titled ‘Swedish Aeroplane Company Limited’.

It was founded in 1937 in Trollhättan and was initially intended to supply Sweden with modern indigenous combat aircraft, such as the -17 bomber and -21 twin-boom fighter.

Saab 91D Safir flight testSaab 91D Safir flight test

After the war SAAB continued to produce mostly military aircraft, such as the Tunnan, Lansen, Draken, Viggen and Gripen jet fighters, although the 340 short-haul turboprop was a significant success, with over 450 built.

The company also began producing cars in the late 1940s, with its first production model, the 92, being notable for its aerodynamic shape.

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Although it handles like a sports plane the Safir was designed as a tourer, so the first thing to examine is the cruise performance. The POH recommends a power setting of 0.8bar/2,400 rpm and the needle of the ASI soon settles on 120kt, for a TAS of 128 at 4,000ft and a fuel flow of around 36 lph.

Adjusting throttle and prop to a more economical 0.7/2,100 still gives 125kt TAS for 28 lph, while pulling the power right back to a thrifty 0.6/2,000 drops the fuel flow to 24 lph while the TAS is still 110kt.

This is clearly not the fastest 180hp four-seat retractable, probably because the blunt nose, wash-out, idiosyncratically-installed wing lights and fixed cowl flaps all combine to produce quite a lot of drag.

On the other hand it is aerobatic which none of its direct competitors are. I confirm the taut handling with some sharp turns and swift reversals, and it certainly is crisp.

Saab 91D Safir flight testSaab 91D Safir flight test

Maybe it’s the military look or simply that I’m flying right-handed, but it really does have that ‘mini-fighter’ feel and I’m tempted to fly a few basic aeros, but as it’s nearly sixty years old, there’s some unsecured baggage in the back, and we don’t have parachutes I decide against it and move onto an examination of the stick-free stability.

This turns out to be positive longitudinally and strongly positive directionally, with neutral spiral stability. For an aerobatic aircraft, it’d be quite straightforward to fly in IMC.

An analysis of the slow speed handling and stall characteristics shows this facet of the envelope to be as satisfactory as every other aspect, with the caveat that the limiting speeds for both the undercarriage and full flap are quite low at only 80kt.

Flaps and undercarriage ‘up’ it stalls at around 52kt, and this drops to 48 with full flap. There is plenty of pre-stall buffet and the stall is very benign. Flaps up, there’s no tendency to drop a wing; flaps down, it consistently dropped the starboard wing, but in a reluctant “I tried to tell you we were getting slow” manner. This really is a very friendly flying machine.

Saab 91D Safir flight testSaab 91D Safir flight test

With the airframe cleaned up I increase power and start back towards Fenland but can’t resist a few more steep turns and sharp reversals. For a four-seater, you can really chuck it about, and the handling is absolutely delightful.

It really is a very impressive machine, and it continues to impress back in the circuit at Fenland. Having slowed to just below eighty, I lower the undercarriage and then extend the first stage of flap.

There’s a noticeable pitch down when extending the split flaps but it’s effortlessly countered with the excellent trimmer. Extending the undercarriage is obviously easier than raising it as gravity pulls the wheels out of the wells.

All is going splendidly until a call from a PA-28 for “long final for 36” (I suspect as far south as Norfolk) puts us so far downwind that I almost lose sight of the airfield. Once the PA-28 appears, we promptly turn base and then final, motoring back at 75, before extending full flap and slowing to 70, with an ‘over the hedge’ speed of 65.

Saab 91D Safir flight testSaab 91D Safir flight test

The air is calm, the breeze not far off the nose, and the Safir simply feels as if it’s on rails. It’s very speed-stable, and if the strip were short I’d have no hesitation in dialling the speed back to 60, although 65 does give me a nice little float to a very gentle touchdown, which I convert to a touch ‘n’ go.

All the subsequent landings are equally easy, and it is with more than a pang of regret that I taxi in and shut down.

A capable aircraft

If you haven’t already guessed, I was very taken by the Safir. It would meet my needs admirably, having the speed, range and performance to carry wife, children and dog comfortably – or I could also fly a few gentle aeros if I were in the mood.

Saab 91D Safir flight testSaab 91D Safir flight test

And just like another of Andersson’s aircraft that I’ve flown, the Bü 181 Bestmann, I couldn’t help but wonder just what a capable aircraft it would make if put back into production.

Lose a bit of weight (and those silly leading-edge lights) add a 200hp IO-360 turning a modern three-blade ‘Scimitar’ prop, make the cowl flaps in-flight adjustable and you’d have one hell of an aeroplane!

Incidentally, John is planning to take 91 Delta on a solo circumnavigation of the globe

in 2020.

To follow his progress, go to www.flyingvisit.org. (Any offers of sponsorship would be greatly appreciated.)

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