MAPICA - Avion MH Broussard

FLIGHT TEST MH 1521 "Broussard" F-BMJO

FLIGHT TEST by Raymond Delaunay. Interviewed by Michel Bénichou. This article first appeared in "Le Fana de l'Aviation " in November 1995 and is reproduced here with the kind permission of the author (Copyright "Le Fana de L'Aviation Nov 95)

One of the indispensable a ccessories for the pilot of a Broussard ( if he does not have the standard equipment : - 'Ladder, folding, fuel tank filling, pilot for the use of ) is a pair of steps or a ladder, in order to control the oil level, on the right of the nose cowling, in li ne with the fire-wall, or to climb on to the wings to fill the fuel tanks

During the pre-flight checks, particular attention must be paid to the counterbalance weights on the ailerons and to the compensation cables for both tail plane and left rudder ( thi s last is automatic but can also be set in flight ) in both cases the breaking of the cables in flight would cause fluttering and eventual rupture of the rudder fin. As for the second, it seems to me that it would be difficult to do without it. The engine cowlings of the Broussard are composed of several panels, on each side, two of them one behind the other, are latched into the upper panel, and locked by the lower panel. As these lateral cowlings are closed, you must ensure that they have not slipped and jammed the cooling flaps ( the non-functioning of these flaps could cause the engine to overheat )

The fragility of the propeller's variable pitch mechanism, means that you must check for oil leaks at the propeller hub - in which case the flight must be cancelled. The propeller is then swung by hand - obligatory for all radial engines.

Climbing on board is easy. The cabin is spacious, the doors are large. The Broussard was designed to compete with the De Haviland Canada Beaver of the same power, if you look simply at the volume available inside the fuselage, and the weight that can be carried, then the Broussard can be considered a complete success. The cabin is practical and easy to access, for up to six people, or for freight when the passenger seats are removed. The pilots' seats are covered in leather, are very comfortable and adjustable. It is recommended to put them into the high position before start-up procedure, the better to see outside. With the seat high, the view out is far better than you woul d expect in a large tail wheel aircraft with a radial engine. The pilot in the left seat and the co-pilot in the right seat, are position much as in a long-distance truck, you have an impression of space which in fact is false, the cabin is far from being a model of ergonomics - especially in a cross wind - but let us not go too fast

After main switch to "on" and the battery on line, the pilot checks that the engine cowling flaps are open 1 cm, propeller fully coarse - and not fully fine as you might expect - throttle fully back, mixture to cut-off, etc. .

The fuel cock, on the floor is opened, and the tank selector is turned to the vertically up position, a movement which gives an automatic opening of the oil cock. The starting of a Pratt & Whitney de 450 hp is simple, as long as no-one touches the throttl e - risk of provoking a fire. Mixture to "normal", throttle forward 1 to 2 cm ( All three levers are grouped together in one block on the sides of the fuselage ) Electric pump "on", fuel is injected into fi ve upper cylinders, the button is situated on the lower left of the panel, 5 or 6 if the engine is cold, 3 or 4 if the engine is hot. At the lower centre of the panel, the index finger raises the security cover of the starter, index and middle finger pull out the choke while the thumb presses on the starter button immediately above. The propeller turns, the pilot counts the passage of four blades and on the fifth, he puts the magnetos to "contact" with his left hand.

The excellent engine usually starts firs t time with a sort of hesitation, as with all radial engines, the upper cylinders fire first, which is normal, they are the ones which had the fuel injections, followed the second time round by the lower cylinders, and the engine 'comes on song'. As soon as the engine is running you need to ensure that it does not go over 800 rpm, with the propeller in coarse pitch, any higher rpm could damage the engine. As soon as the oil temperature reaches 40\'b0 , the propeller can be moved to fine pitch, the oil pressure checked again.

The Broussard engine, like others, is started in coarse pitch to save wear on the fragile leather piston seals in the pitch control cylinder ( 1 ), which is fed by engine oil. As you know when the propeller is in fine pitch, these pistons are under pressu re. In order not to ask these seals to work with the engine oil cold and thick, the propeller is maintained in coarse pitch until the oil has reached a more fluid state. Later during the engine checks, the fragility of these seals imposes a c ertain dexterity in using the pitch control lever.

The oil temperature is regulated by a brown-knob lever at the bottom of the panel. The correct cylinder-head temperature between 160 and 260° C, is regulated manually as well by flaps on the engine cowling. These flaps are operated by electric motors which can fail if operated too brutally.

Taxying is simple with the engine set at 1.200 rpm, maximum, more than sufficient for taxying. The disc brakes operated from the left seat rudder bar only, allow easy st eering. On wet grass, however, the bakes must be used with caution to avoid locking a wheel. The aircraft would easily spin on itself, the free castoring tail-wheel would not help to maintain a straight line.

For take-off the seats are lowered, the flaps are set at 15\'b0, mixture full rich, the throttle opened till admission pressure stabilises at 125 pi\'e8 zes, the propeller turning at 2.300 rpm. There is a high noise level despite headsets, high vibrations - normal with this type of engine. The supersonic whine of the propeller, so strident to those on the ground, remains unnoticed inside the aircraft.

The Broussard keeps a straight line on take-off because the prop wash passes directly in between the twin tail (3) The flight manual says to push forward on the stick to get the tail up. Personally speaking, I find that you need to give a very real push f orward......

Surprisingly the effort is much more important than when on the ground. At 65 Kt. \par ( 120 km/h ) the Broussard takes off all by itself. In zero wind c onditions the take-off run is fairly long, but in a light head-wind take off is at 50 Kt. ( 92 km/h ) In a cross wind you have to be careful, the aircraft will weathercock into wind in no time and leave the runway by the side door. However the rudders are by now efficient enough to correct any swing.

Once airborne, a short period of level flight to allow the speed to build up, the admission is reduced to 117 pi\'e8zes and 2.200 rpm. Climb out is at 105 Pz and 2.000 rpm, but the reality is far below the 1.000 f t / minute mentioned in the flight manual. At 300 ft the electric pump is switched off ( 4 ). The raising of the flaps gives a marked nose down effect, easily countered, but you need to be pretty quick to change hands and spin the compensator below the ri ght hand ( 5 ).

The engine growls away and the large carburettor air intake sitting on top of the cowling tends to spoil the view. Visibility is in fact very good, far better than you would expect from high wing aircraft. There are three possibilities offer ed for the cruise : -

Economical at 85 Pz, 1.800 rpm gives around 90 Kt. ( 165 km/h ) \par Normal at 88 Pz and 1.900 rpm gives a fuel burn approaching 80 l / h, but where the speed does not want to reach the 100 Kt. ( 185 km/h ) shown in the flight manual.

High at 93 Pz, and 2.000 rpm with 90 l / h the Broussard will cruise at around 190 km/h. Not a lot for 450 hp. But the Broussard comes into it's own with the 1.000 kg of freight that it can carry.

When a stable speed in level flight is established, the mixture is pulled back to "normal". In flight the Broussard is slow and sufficiently stable to be able to release the controls to relax arms and legs. The major preoccupation of the pilot - what there is - is to control oil and cylinder-head temperature by means of the engine cowling flaps. With a little practice the pilot can see at a glance if the flaps are open enough, knowing the ambient temperature. Hr does not need the temperature gauges on the panel, except to check that the needles are where they should be . Contrary to what one might think about them on the ground, the Broussard's controls are heavy - very heavy, even. The ailerons are pleasant to handle, better than one sometimes hears about the aircraft, firm, a little slow, but replying immediately and precisely, giving the illusion that the Broussard is highly manoeuvrable.

As long as one is in normal flight, the weight of the tail plane is not really a problem, for it is used with very little movement, but as soon as you try to tighten a turn to ensure no loss of height, it becomes hard work. The Broussard is very nose-heavy, the fault of the Armée de l'Air whose modification moved the engine forward by 10 cm. But it is the rudder that I am most careful about, to the point where I refuse to put the Brou ssard into steep turns. It responds with a slowness that the ailerons and tail plane do not have, especially at low speeds. Maybe I am too careful, for pilots with many hours on the Broussard can make it perform lazy eights ( 6 ) or even side-slip on fin al s. It is not possible to side-slip with safety, an aircraft which does not have a good lateral control ( 7 ). Perhaps it all stems from when I was a student pilot, I was very impressed by the Broussard, I never imagined at that time that I would ever fly one.

I can still hardly believe it - even today when I can do lazy eights with it - even if I feel at ease at the controls, this machine continues to impose respect on me. this means that there is not very much you can do with this aircraft, the limits of s peed are very narrow, and it tends to drop the nose as soon as you reduce the power, cruise at around 100 Kt. ( 185 km/h ) and stall 65 Kt. ( 120 km/h ) flaps up (8).

It is not surprising that according to the flight manual : "Aerobatics are strictly prohibited on this aircraft"

The Broussard is in fact a truck. Considered as just that - a flying truck - and it is a good aircraft.

At the stall, the ball in the centre, the nose comes up to about 30\'b0 and then drops. At a higher inclination the nose drop is more pronounced, with a height loss of 150 ft. Voluntary spins are forbidden.

It is at the landing that the Broussard has certainly acquired it's deplorable reputation. It is prepared quite normally, mixture full rich, inlet pressure reduced to 60 Pz , speed at 80 Kt. ( 148 km/h ). It is possible to bring it in at 75 Kt., but as yo u are more likely to lose speed rather than increase it, a security margin is useful. 80 Kt. must not be exceeded. Flaps at 20° produces a strong nose up attitude which can only b e countered by a firm push on the stick before resetting the compensator. On the turn on to finals, the Broussard enters into it's most dangerous phase, because at low speeds the rudder is at it's least effective. To start the low angle bank ( 20\'b0 ) and a t low speed, I co-ordinate the stick and rudder on the same side. The Broussard banks but hardly changes direction : it slips, the ball which indicates if the flight is symmetrical slips towards the inside of the turn. This incites the pilot to push even ha rder on the rudder - exactly that which he must not do, for 2 or 3 seconds later the ball will quite simply return to the middle. which shows that it is not the pressure on the ruder bar which is insufficient, but the inertia of the tail of the aircraft. In fact the reflex to push harder on the rudder bar leads after a moment or two to a fierce skidding in the opposite direction, which could have catastrophic consequences.

On long finals the engine cowling flaps are closed to avoid a too rapid cooling of the cylinder heads ; the compensator is set generously nose high, the propeller is set to fully fine, flaps to 40\'b0 . Still at 75 Kt., the aircraft drops very quickly, you need a fairly steep glide path so as not to land too short. It is unnerving the first t ime you land a Broussard. It is important to know the aircraft well so as not to be surprised by the flare, which is the "sporty" part of the flight. To put the aircraft parallel to the runway, you need to pull back on the stick progressively. But, the Br oussard is so centred forward ( nose heavy), that with 100 l of fuel and solo pilot, the effort of pulling back with both hands is shattering ! If you have a co-pilot aboard an otherwise empty aircraft, the co-pilot is expected to sit at the back of the cabin to help with the flare. W hen the cabin is full of either freight or passengers, then the flare is easier, though the effort remains high. When the stick is held in both hands, it could be dangerous to release one hand to move the throttle for example ; the risk is high that the stick may shoot forwards, allowing the aircraft to drop even faster, touching the ground with the nose too low, rebounding and eventually passing on to it's back. Whatever the Broussard does after touching the ground, it is rare that it does not bounce - but you must never release the back pressure on the stick, otherwise the aircraft will continue to bounce harder and harder. this kind of accident was very frequent.

As soon as possible the flaps are retracted to help keep the airc raft on the ground, unfortunately to reach the flap lever you need to reach forward with the left hand - thus taking one hand off the stick... Happily the Broussard, excepting when it rebounds a little high, runs fairly true on roll out. It is sufficient to wait for the bouncing to end, the stick fully back, before braking - gently - to avoid tipping the aircraft on it's nose. An tip to avoid bouncing, do not fully close the throttle, leave on just a trickle of power on, just enough to feel it under your hand, before cutting the throttle completely at the moment the wheels touch. It is important that the compensator is set to nose high - you need all the help on your side to reduce the weight of the stick.

On the roll out the seat is raised. To land a Broussard loaded is easier, but a 'three-pointer' when empty is possible. It is almost as much chance as know-how, I think, but how nice it is when you succeed. The problem of the Broussard stems also from it' s undercarriage, whose legs are simply two blades of steel which together make a very efficient spring : they dampen the landing very well, but straight away return the energy upwards ! The finesse of the gas flame till the last moment allows you to reduce to a minimum the risk of bouncing. It works but on condition that the pilot is well trained and can feel the reactions of his machine. Cross-wind landings pose no real difficulty, except when the wind is from the right, here the pilot's leg is trapped by the trim wheel, and prevent the stick going hard to the right.

Back on the apron, the peculiarities of the Broussard are the opening of the engine cowling flaps, then at 1.700 the propeller goes to fully coarse. The engine rpm is reduced to 800 during the time for the T's and P's to stabilise. Then bring back togethe r the throttle and the mixture to the stop. The mixture lever is thus brought to the cut-off position, the engine stops by itself... cut the contacts, cut the electricity, close the fuel and oil taps...When the engine has fully cooled down, the pi lot must come back to his aircraft to close the engine cowling flaps. The Broussard is the prototype of the aircraft you need to fly regularly in order to master it. For a private pilot such as me, it is an aircraft that must be taken seriously, it will n ot half-measures.R.D.

( 1 ) The pilot controls the propeller pitch via electric motors or hydraulic pistons. In flight the settings remain constant thanks to the movement of the counterbalance weights, maintained in place by centrifugal force. This movement m odifies the pressure against the pistons or the rotation of the electric motor ( Ed. )

( 2 ) The tail-wheel is free castoring. It is free to spin around it's axis. It can be fitted with a locking system - not on -JO, or a system of springs which bring it back to a central position..

( 3 ) The cork-screw effect of the propeller wash against one side of the rudder, tends to want to push the aircraft that way. The pilot stops this by pushing on the opposite rudder bar. ( Ed. )

( 4 ) The electric fuel pump is always 'on' for both take-off and landing. ( Ed. )

( 5 ) On a high-wing aircraft such as the Broussard, the air flow is deflected downwards by the extended flaps towards the tail-plane. Now the tail plane is already negative lift ( it pulls downwards to improve the stability of the aircraft ) When the fla ps are down the negative lift of the tail plane is increased, causing a pronounced nose-up effect ( and inversely when the flaps are raised ) A compensator is a small flap let into the trailing edge of the tai l plane, it serves to reduce the physical effort required by the pilot. ( Ed. )

( 6 ) The lazy-eight is a series of climbing turns. ( Ed. )

( 7 ) Of which the rudder is not efficient. ( Ed. )

( 8 ) Flaps down, the stalling speed is lower. Here it is a normal stall, wings horizontal. In a turn, the more the aircraft is banked, the higher the stall speed. At 60° of bank, the stall speed of the Broussard is over 90 Kt. ( 166 km/h ) higher than the normal cruise speed ! ( Ed. )

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