Stinson were a Michigan based company founded in 1926. They soon produced the first American cabin monoplane suitable for all year round use in 'northern' latitudes. By 1939 Stinson had become a subsidiary of the Aviation Manufacturing Corporation who also owned Vultee and Lycoming. In 1940 Stinson became a division of Vultee and not long after a division of Consolidated-Vultee (Convair), but both owners perpetuated the Stinson brand. Consequently Stinson entered and exited WW2 as one of the largest U.S. manufacturers of light aircraft for civilian and military use.
The Voyager began life in 1939 as a three seat flivver powered by a 75hp engine. It was an expensive aeroplane with a slotted wing and flaps at a time when both were considered extreme luxuries in 75hp aircraft. Partly to cover up the fact that it only had 75hp it was marketed as the Stinson 105 Voyager. It sold O.K. but it was obviously underpowered and early in 1940 it was replaced by the Stinson 10 Voyager with a wider cabin and engine options up to 90hp. Again it sold quite well but Stinson ended production for the civilian market in December 1941.
The post war civilian market wanted more powerful aircraft and so in 1946 the Voyager was marginally redesigned to become the four seat Stinson 108 Voyager powered by a 150hp Franklin engine. Almost 2,500 of these sold like hot cakes. In 1948 the 108 and hardly different 108-1 gave way to the 165hp Stinson 108-2 Voyager of which about a thousand were built.
However it was soon apparent that the original design could not handle all this extra power without constant rudder inputs and so in December 1948 the 108-3 went on sale. This had a much bigger tail with a bigger rudder and the rudder now had a trim tab to help the pilot control the extra torque and p-factor of the bigger engines.
The new big tail Stinson was economically superior to the Fairchild 24 Forwarder which had been its main rival and more or less caused Fairchild to exit general aviation. There was no 108-4 and the 1949 model 108-5 offered a 180hp engine. The flight dynamics supplied are for the 165hp Stinson 108-3 Voyager which was offered for delivery from December 1st 1948.
Two days earlier Convair had sold Stinson to Piper who had no intention of perpetuating the Stinson brand.
The aeroplane Piper wanted was the 'Twin Stinson' which they would soon rebrand as the Piper Apache. The Voyager was already suffering stiff competition from the economically superior and more modern Cessna 170 and it only survived into 1950 before Piper killed the Stinson brand for good. By that time they had produced getting on for 2000 'big tails'.
The 108-3 Voyager was a good aeroplane that sold well, but compared to its simpler post war Cessna and Piper competitors it was slightly tricky to operate. It was however a much better STOL aeroplane than the Cessnas and Pipers, and a better long range tourer. It wasn't a good aeroplane for poodling around in, with no significant payload, for an hour on a Sunday afternoon. It was an aeroplane designed to haul a fairly big load, quite a long way, quite quickly, at a price.
The Franklin engine was at the heart of that. It was particularly high revving and although it was perfectly safe to run the Franklin at low rpm it shortened the life of the engine. The 165hp Franklin B3 in the 108-3 could really only compete with the Continental or Lycoming if it was revved hard and it really liked to be operated only in the 2500 to 2600 rpm range. Throttling back to less than 2500 rpm saved fuel, but engine maintenance costs tended to rise faster, so economical cruising is at 2500 rpm. Care should be taken not to exceed 2800 which is the 'emergency' rating. The engine can deliver 165hp for go around, but with a fixed pitch prop that is the only time we should invoke 2800 rpm and we will struggle to get that.
The B3 was a genuine 165hp engine, but only when fitted with a variable pitch screw. These were optional on the 108-3 but they added significantly to overhaul costs so most owners chose the fixed pitch option and that standard option is the one replicated in these flight dynamics. With a fixed pitch screw the engine is rated at 150hp, but 165 are in there if we can get the revs. It will only deliver about 2300rpm and the rated 150hp when we rev it up against the brakes before take off.
The Franklin wasn't really 'tricky' more a case of being 'fussy'.
Most general aviation aircraft come with a brochure that is little more than a con trick. They tell us how much the aeroplane will carry and how far it can fly on full tanks. ,but fail to mention that the payload with full tanks is negligible. The Voyager wasn't like that. It could carry max payload and max fuel at the same time and unlike most general aviation aircraft which make that claim it had pretty big fuel tanks. That was just as well because running at 2500 plus RPM the Franklin is quite thirsty.
The trick to getting good cruising velocity out of the Voyager is the same as in any other aeroplane. It must be flown as high as possible, in the thinnest possible air, subject to not exceeding 12,000 feet QNH as it is unpressurised and has no oxygen supply. The Franklin must not be cruised at full throttle below 5000 QNH, but is fully intended to cruise at full throttle as soon as we reach 5000 QNH and that is how the Voyager should be flown.
We have 300 pounds of fuel, 24 pounds of which are unusable by design. At 5000 feet and full throttle we will burn 65 pounds per hour (PPH). That will give as four hours at 110 KTAS (126 MTAS) with a tiny VFR reserve. If we throttle back to 2500 rpm and cruise much higher than 5000 QNH we can obtain 94 KTAS (108 MTAS) burning less than 50 PPH allowing five hours with a decent VFR reserve.
Five hours in a cabin this size is enough for most passengers, even those who enjoy touring by air.
This aircraft is not cleared for flight in known icing and that will compromise our ability to fly high some of the time. Nor is this aircraft equipped for IFR. It is however a very genuine four seat VFR tourer with good range covered at a decent velocity. The payload is substantial. Even with full tanks we can carry 780lbs which is four standard FAA adults each with 25lbs of baggage. Whats more there is actually a big enough baggage locker to hold that baggage. And we can get the fuel and the payload into and out of small fields with trees at either end.
This brings us neatly to the aerodynamics and handling.
The Voyager always had a slotted wing and powerful flaps even when it only had 75hp. These devices allow the Voyager to climb away steeply over trees. (or a ridge line). ahead and descend steeply over trees near the landing threshold. Quite apart from the fact that steep approaches require more skill than shallow approaches the Voyager has some extra 'issues'.
The original intention was to have only one flap setting which would be used for both take off and landing. However that flap setting imposed so much nose down trim that the elevator ran out of authority to flare the aircraft for landing! This was especially true when the engine was throttled right back or had failed and there was no propwash over the elevators.
Consequently a tiny additional second stage of flap must be deployed before landing. This actually imparts further nose down trim, but it is there to pull the elevator interlock. Once we extend FLAP 2 we can get extra up elevator travel. That extra travel would be dangerous at high speed and our ability to apply G when we do not have FLAP 2 extended is deliberately compromised by the interlock. The 108-3 Voyager has quite poor elevator authority until FLAP 2 is deployed.
FLAP 1 is 27 degrees and all 27 degrees are used for take off. Together with 13% nose up trim this enables a very steep climb gradient over any obstruction at the end of the runway. Once we are above the obstruction we retract flap and accelerate.
Now we must come to terms with the fact that this is essentially a 75hp flivver from 1939 with a 165hp engine shoe horned into it. We now have a big tail and rudder trim to compensate, but this airframe was never made to handle that much power, and nor were the flaps.
Structural failure is likely at 158 MIAS and if we exceed 126 MIAS the probability of structural failures increases steadily. We may need to moderate power to prevent overspeed more often in the Voyager than in other general aviation aircraft. At this point the Franklin becomes a potential embarrassment. Ideally we want to keep the revs up to 2500 whilst descending, yet we should aim to avoid exceeding 126 MIAS in descent, especially if we are in turbulent air, or may encounter turbulent air.
Consequently top of descent requires careful planning, because the descent should be shallow and fast at 2500 RPM and 125 MIAS. We also aim to use 2500 RPM in the circuit for as long as possible so we will be flying most of the circuit at just under 110 MIAS.
Now we must come to terms with the fact that the pre war flivver heritage of the Voyager means that the flaps are critically weak. Since FLAP 1 and FLAP 2 are hardly different they have the same profile drag limit which is just 88 MIAS. Consequently late downwind we must reduce below 2500 RPM and slow to 85 MIAS in level flight. We must sustain 85 MIAS until final when we extend both stages of flap in time to achieve our reference speed which is 70 MIAS no later than 50 feet above ground level.
Remember we must deploy FLAP 2 (33 degrees) for landing to pull the elevator interlock so that we can get the nose up in the flare. FLAP 2 makes little difference to our descent profile or trim. With any flap deployed descent is steep. The less experienced we are the earlier we should establish Vref = 70 MIAS with FLAP 2 deployed and trim for that IAS. Once we are trimmed for 70 MIAS with FLAP 2 deployed we can concentrate on sustaining the steep glidepath to the touchdown point with power. We must not use the yoke to control rate of descent. We must use power to control rate of descent whilst the elevator trim holds the aeroplane at Vref = 70 MIAS. Elevator trim *never* controls pitch. Elevator trim *always* controls IAS. There is no such thing as pitch trim.
Being able to fly the 108-3 Voyager well, and being able to make the most of its STOL capabilities, is all about acquiring the skill of trimming for a given IAS and using power alone to control glidepath. We should practice making long descents at Vref away from the airfield until we are confident that the aeroplane will fly itself at 70 MIAS once we have trimmed it to do so. Then we can concentrate on placing the touchdown point correctly in the windscreen with power, as IAS takes care of itself. Once trimmed for Vref we use the yoke only to flare.
Of course the weak flaps are a potential liability after take off too.
Although we use only FLAP 1 for take off that is 27 degrees and the profile drag limit is still just 88 MIAS. We must climb steeply whilst we have flap deployed and we aim to keep our IAS in the 80 to 85 MIAS range. Once we are clear of obstacles ahead we retract flap and accelerate to 95 MIAS which we will use to maximise climb rate after we no longer need to restrain climb rate to maximise climb gradient.
FLAP 1 imposes significant nose down trim which we counter with significant (13%) elevator up trim during the take off. After we retract flap we must restrict climb and accelerate to 95 MIAS removing elevator up trim to sustain 95 MIAS clean as we do so.
Now we encounter the Franklin again. Have you figured out why the Franklin went out of production soon after the Voyager yet?
It is permissible to run the Franklin at more than 2600 RPM and we will if we can in a go around situation, but more than 2600 RPM shortens engine life so in the climb out, (which should ideally be to an altitude of 5000 QNH or more), we either make sure we climb steeply enough at 95 MIAS to keep RPM below 2600 at full throttle; else if we intend to cruise climb at a higher profile drag we should retard throttle to 2600 RPM in a high drag shallow climb.
One good thing about the Franklin was that it wasn't fussy about temperature control. If we observe the RPM restrictions, temperatures and pressures will take care of themselves though we must check them every so often to ensure that the engine is not malfunctioning.
Take time to study the three point landing attitude, versus the horizon, from inside the cockpit before flight, and flare to that attitude for touchdown.
FS9 users without rudder pedals are advised to set p-factor, torque and gyro effects to minimum in the FS9 realism screen. The Franklin had manual mixture control, but FS9 users who have no real world experience of leaning aero engines are advised to turn automixture ON in the realism screen.
Now please read the supplied handling notes. The 108-3_ref.txt version is for printing and the htm version will be used by FS9 on screen. Make sure you can relate the one line reminders in those handling notes to the content of this document.
Don't worry the Voyager is actually a stable, nicely damped and fairly easy to fly aeroplane. It just has certain quirks which we must learn to live with and control. After all thats what flight simulation is all about. Enjoy.
