Double fatal at Watts Bridge

[Guest TOSGcentral]

There are no indications of any structural failure, other than that caused by the impact - in fact the Falke was in a state of excellent condition and maintenance - I have flown a lot tattier examples.

 

You are not over-stepping any mark Motz. We are keeping things neutral, not talking about personalities, not allocating blame or responsibility - you are simply asking some technical questions and I am answering them

 

 

[Guest Baphomet]

Hi Tony, the thing I find most curious about this, is that the report stated the passenger had been thrown out of the aircraft. I notice from the photo that the passenger harness is in place, do you know if it was serviceable? A possible scenario (pure speculation) that springs to mind, is pilot in command suffers a seizure falls forward jamming controls - passenger releases harness to try to assist/regain control but runs out of time - aircraft impacts the ground, and the passenger now unrestrained, is ejected from the aircraft. No doubt the inquest will establish if any of this may be plausible.

 

Again, this is pure speculation on my part.

 

Whatever the cause, a very sad time for all.

 

 

[Guest TOSGcentral]

The passenger harness was perfectly serviceable as was the pilot's. I inspected them and their mountings most carefully - they were in as new condition.

 

The passenger harness was not being worn at the point of impact - hence the ejection.

 

I personally consider that a good quality post mortem is now an essential part of this investigation - which is why I have been quiet about the subject because it does indeed draw us into speculation and opinion. That could be dangerous ground to wander onto if taken (or written) the wrong way.

 

My compliments Baph on what you wrote and the expression that you used.

 

 

[Guest Andys@coffs]

Tony

 

Was the direction of side slip consistent with a passenger leaning towards the LH seat, which I pressume would result in pressing the passenger right foot pedal?

 

Its an interesting point that extends on a previous debate around teaching our passeengers some aspects of staying alive if the pilot were to be incapacitated. It just goes to show that the incapacitation timing, and the resultant time available for a passenger to react appropriately means to a cirtain extent its still a bit of a lottery..... buit like the rest of life....

 

Andy

 

Andy

 

 

[Guest TOSGcentral]

Yes Andy - that would be entirely consistent.

 

But some additional information about a Falke cockpit.

 

1. There are smooth floorboards prior to the rudder pedals so there is nothing to lodge your heels against to keep your feet clear of the pedals and you can relax (one of the trying parts of instructing in them as there is not a lot of room).

 

2. There are two large grab handles each side of the cockpit above the instrument panel. One of these is quite clear in the image. The passenger side one is there but less obvious unless you know what you are looking at.

 

3. The two occupants are sitting shoulder to shoulder. One reaching the other is no drama. When instructing on these aircraft I was easily able to (on exercise) demonstrations) fly the aircraft through the student's hand on his/her stick.

 

4. The pilot of this Falke was most adequately strapped in. I do not see that he could have 'slumped over the controls' it is not physically possible - neither was it even after that terrible impact.

 

5. Any medical event (if any such happened) could have equally been with either of the occupants.

 

 

[Guest J430]

Just a thought Tony, I see you have pointed out several times the flight controls were not appearing to have failed.

 

My aircraft partner tells the story of his first instructor 40 years ago who was killed later on doing aerobatics. What killed him? A 10c piece!!!

 

Could there have been an obstruction that jammed a control and subsequent to the crash come free and therefore removing the evidence?

 

J

 

 

[motzartmerv]

Yea, i read a story recently (can't remember where) about a glider pilot who was fine tuning an instrument in flight. Which involved useing a tiney screw driver. It was quite bumpy at the time and he accidently dropped it. He could feel it in the controls as it had dropped down into the pushrod housing between his legs. He took is harness off to get a a grip on the screwdriver, just at that moment a thermal kicked the plane sideways and he leaned on the stick which put him inverted. So he was fully resting on the canopy and trying to right the acft..It didnt work and the canopy gave way and he "FELL OUT".. luckily he had worn his shoot and made an uneventfull float down to earth while watching his pride and joy spin in.

 

The only connection i can see is the harness was off.. but still.. perhaps and avenue for enquiry..

 

cheers..

 

 

[Guest TOSGcentral]

J430 & Motz.

 

 

Yeah that is an event that can happen.

 

 

Let me explain a little more about the Falke cockpit. You are sitting on essentially a space frame open, main structure floor that the seats are bolted to. The belly of the aircraft is quite deep below this, reaching out in a tubular cradle that the single main undercarriage wheel is mounted to.

 

 

Basically you have the crew and the control circuits ‘suspended in space’.

 

 

You are not looking at a scenario where you have some object under a door that you are trying to open – and jams the door very firmly when wedged against the floor.

 

 

However it is conceivable that a foreign object could have been dropped into the elevator circuit. When you are sitting at the table rolling dice with Lady Fate then a fraction of a percentage of chance can kill you. That is what we face because we fly and that is why Airmanship , expressed in Airworthiness and Operational conduct ,is there to reduce those odds in our favour.

 

 

The cockpit was such a mess that it impossible to say if such an event happened and you may find a foreign object but who is to say if it was involved once it is dislodged and now laying about – unless in a very sealed environment?

 

 

Now – we are running up to the fine edge of the wedge and I want to say a few things.

 

 

This thread has probably been the most informative of any thread on this forum and has been operating quickly – we are only 4.5 days from the event.

 

 

It is a demonstration that FACTS can be presented (if known) and background facts may also be put forward to assist in opinion. All of us can only gain from that and that is what I would like to see this forum achieve in the future.

 

 

We are now on the knife edge of going into speculation! I am prepared to deal with that as best I may and answer questions even if they are speculation on where we now are at – because we yet do not know!. But this thread IS NOT going to devolve into any opinion of conclusions because that is not our province or authority. Neither will it address either of the crew of that aircraft directly!

 

 

In conclusion I would like to thank the sensitivity of ALL the posters. This has been a demonstration that we can get it right and that we can get value from discussion.

 

 

Aye

 

 

Tony

 

 

[Ben Longden]

Hi Tony,

 

My condolences to the familes and friends concerned.

 

I have to say I am impressed with the way you are handling this. Bloody professional, and I like the way that questions are being asked by members and everyone is avoiding speculation and blame. Top stuff.

 

I also liked the tasteful photos. The kids could read this story, and not get nightmares, but actually learn from it.

 

Ben

 

 

[Guest TOSGcentral]

Flight Path Replication

 

This morning I replicated the final stages of the Falke’s last flight according to the eyewitnesses. This was the first morning that also replicated the flight conditions at the time.

 

 

I used a T500 Thruster carrying sufficient residual power to replicate the overall performance of the Falke itself – Falkes being somewhat in short supply around here.

 

 

I took plenty of fuel to get the weight up plus Lois came with me for additional load. However I was probably at least 200+ kg short of the Falke’s flying weight.

 

 

I was flying one hour earlier than the actual crash time and, as expected, the air was just becoming unstable with very mild bumps. We have had a new air mass in and I think that I obtained very similar flight conditions via the time adjustment. Wind speed was 3 knots at the surface which was also about right.

 

 

At 250’ and approx 200 mtrs from the impact point I initiated a yaw to starboard then pitched the nose down and held it there until approx 30’ agl (don’t try this at home please!)

 

 

The following factors were most plain:

 

 

• In the space available it was difficult to get the Thruster above 30 degrees nose down pitch without a reasonably savage pitch change that was not really observed by the eyewitnesses.
   
   
  
• There was a great deal of ‘ground rush’ and visual stimulus to get the aircraft out of the dive much earlier than I took it to.
   
   
  
• At the approach speed (60 knots that I used and would be typical for a Falke) the crew had less than 4 seconds to do something about the situation.
   
   
  

 

 

From this exercise I conclude that there is a high probability that the Falke was under a continuing nose down pitch influence and was probably steepening its descent path rather than abating it. That however is merely my opinion.

 

 

Any such continuing pitch down influence would have been relatively gentle in nature rather than an abrupt and vast ‘forward shove on the stick’.

 

 

[pylon500]

Having read a report on an incident involving a control mix-up with a centre stick aircraft (I've flown Falkes, I know they're twin stick) could it be possible that there was a momentary mix up between the stick and the spoiler lever?

 

Scenario; Aircraft high but slow, enters strong sideslip with partial spoilers, encounters wind gradient and increases decent rate, PIC intends to close spoilers (forward motion) and pitch up (rearward motion), but for a split second confuses which stick is which and pulls full spoiler while shoving the stick forward?

 

Inspection would need to be made of the stick mounting point to try and determine which stick had the most weight at the time of impact?

 

The fact that the passenger was unrestrained is puzzling.

 

Sorry if this is out of line.

 

Arthur.

 

 

[Guest TOSGcentral]

G’Day Arthur,

 

 

The scenario you portray is of course a possibility but not a high probability (a) because the PIC was experienced on type and (b) because there were no significant wx considerations to put any unusual control demands on the crew.

 

 

However to examine the situation fairly for the benefit of readers not familiar with the Falke it is worth explaining the controls because they are a little unusual.

 

 

There are two control columns on the Falke that each person has between their legs. These are connected laterally by a yoke arrangement below your legs and then have the conventional central torque tube running aft from the centre of the structure.

 

 

There is a single push pull throttle control mounted centrally in the instrument panel that can be reached with equal ease by either occupant.

 

 

The spoiler control is also duplicated but the two levers are quite different and neither is anything like the stick.

 

 

The lever for the left hand seat is quite large, has a hooked top and is mounted on the cockpit’s Port wall. This is totally out of reach of the right hand seat occupant.

 

 

The duplicate control lever is centrally mounted but it is quite different. It is much shorter and thinner. This is equally accessible to either occupant but does not come readily to hand and you have to really reach for it. This is irritated by the spoiler springs being quite strong so some considerable pull force is required to open the spoilers and then keep them open. The smaller central lever has barely adequate mechanical advantage so for the occupant of the left hand seat it is more comfortable to use the larger left hand lever.

 

 

So – for the right hand seat the aircraft is entirely right hand control and the left hand being used for the centrally mounted services (throttle and spoilers and trimmer).

 

 

For the left hand seat occupant the aircraft can be operated entirely left handed with the right hand being used for the central services. But it is more pleasant to change hands for approach – and this is the main difference on the Falke so is worth examining a little more.

 

 

You really need three hands to have total control of any motor glider. If you conventionally keep your hand on the throttle as is normal with powered aircraft operations then the glide performance is too high and the drag too low for a normal throttle controlled approach and the machine will float for ever on ground effect when it eventually gets to the ground. So you have to use the spoilers or airbrakes to ‘dirty’ up the machine so that approach control may be effected.

 

 

The standard technique is therefore to position the aircraft at the final turn (500’ agl) at approach airspeed (typically 55-60 kts on a Falke) in position where it will comfortably over-shoot (reach the far end of the runway). The throttle is now closed completely and the engine left idling (if in fact the engine is on at all because it need not be).

 

 

The left hand seat occupant on the Falke can now change hands on the stick and access the left hand spoiler lever then make a conventionally controlled full glide approach.

 

 

The left hand driver therefore gets plenty of practice at flying with either hand and doing different things with both hands at the same time.

 

 

In ab-initio training this complicates things for the student and life becomes both busy and confusing for them – particularly on a Falke that is a bit enthusiastic about bouncing on landing unless fully held off (not enough prop clearance to wheel land them during training).

 

 

This was of no particular account as we were using the machines to speed training for pure gliders. So the student was stuck in the left hand seat and was not involved in any engine control at all – it was a straight forward stick, rudder and spoiler control affair, all right hand flying, with no hand changing required.

 

 

In the situation that obtained in the fatal the experienced Falke pilot was occupying the left hand seat and the ‘passenger’ was anyway proficient at flying with either hand.

 

 

I do not know if the pilot was an instructor but let us hypothetically say the ‘passenger’ was being given some familiarisation on the controls just so we may explore that area a little.

 

 

The Falke is a very docile machine – it is a basic trainer! For a normal power pilot it does have marked aileron drag that requires rudder/aileron co-ordination but at worse that initially involves only a bit of wallowing about – nothing that would significantly effect overall control.

 

 

The only really new thing would have been the pitch down via spoiler deployment. Now the Falke spoilers are not terribly effective and the normal spoiler deployment pitch-down is certainly there but not particularly drastic. The view forward on approach is excellent and the broad top of the instrument panel gives a great attitude/horizon reference.

 

 

On the other hand if a large and fast spoiler deployment were used then seeing the nose down pitch for the first time may have come as a surprise. More to the point if the passenger were not restrained by the harness then there would have been a reduced G situation and an instinctive bracing activity.

 

 

That would have been bracing by the feet (that would have maintained the slip that had been established and equally likely letting go of the stick entirely to take hold of the large grab handle right in front of you, while hanging onto the fully deployed spoiler lever for additional security.

 

 

Stick free the deployed spoilers would have continued the nose down pitch and we would have had exactly the flight path that appears to have happened.

 

 

However that is not likely! The pilot would not have just sat there and accepted the view that I took a close look at yesterday morning – it was very motivational. It only required that the stick be pulled back because the elevator has massive authority over the spoiler deployment pitch-down. At the very worse the Falke would have bellied in rather than have dived in.

 

 

That is of course if the pilot had not already been incapacitated and the passenger had been left with the lot.

 

 

I want to say a few words about speculation. It is possible to contrive convincing explanations for what may have happened in any situation and that is fair enough as long as no conclusions are drawn – because we all want to learn as much as we can to prevent the same thing happening to us – but we are only speculating.

 

 

I have gone into some detail here and for some readers that will have added to their knowledge base about how motor gliders tick and the Falke in particular. But that is all I have done. We will have to wait for the investigation to proceed and an official reason to be published.

 

 

[icebob]

Hi Tony,

 

Thank you very much for the explanation of the motor glider it has helped me, I am sure others too who are not fermiliar with this aircraft and for me it has put some of the pieces into place.

 

I can relate to the spoiler issue as startling on your first flight. I have just started some gliding.:thumb_up:

 

Bob.

 

 

[Guest Mike CMB]

Gotta have a go

 

Tony ,

 

Firstly let me thank you for all the above which has been most informative. I have been flying gliders on and off for 38 years and have a few hours up on most types.

 

I have either seen or read about a few accidents during this time. I remember well an accident at Kingaroy in the 70's when a an Open Libelle exceeded its maximum velocity and broke up in the air. I remember hearing a bang and looking up to see what turned out to be the wings flutering down. At the time there were lots of theories what caused the accident and being the first fiberglass aircraft to break up in the air all sorts of wild suggestions were put forward. In the end the autopsy showed the pilot had a heart attack.

 

The late Maurie Bradney told me about his accident when a Twin Astir had elevator failure on take off at about 200 ft. Maurie had the presence of mind to push hard rudder so the wing tip hit first and the wing absorbed most of the impact. He survived the crash although seriously injured.

 

The common link to the Watts Bridge accident is firstly pilots do have medical emergencies while in command. Secondly the will to live makes us fight for any chance of survival no matter how slim.

 

Most of us would have a go if we thought it may improve our chances even if it meant taking off our harness.

 

Mike

 

 

[Guest L/D]

Tony,

 

A recent flight test (in a SF25c by a 5000hr Falke pilot) with different configurations (because of this accident) indicated that a side slip followed by opening airbrakes pitched the nose down around 25 degrees in 2 secs.

 

The Falke is indeed a very docile aircraft and can and is a lovely aircraft to side slip in just prior to round out. In this configuration and being low off the deck, the above scenario could also result in a less than fortunate outcome.

 

I am not saying that that is what happened, I am saying that it doesn't matter how docile an aircraft is, there are situations where most aircraft show adverse reactions to what you are used to. (Like a C180 until you lock the hangar doors on it!)

 

 

[Guest TOSGcentral]

Hi L/D,

 

 

Thanks very much for that post as it rounds up a bit more of the scenario of understanding possibilities. It is very much what I would have liked to do myself as I have not been back in a Falke for a long time – but the Thruster of course does not have any spoiler or airbrake system at all so I could only look at the flight path that had been observed.

 

 

Perhaps you would convey my personal appreciation to your test pilot?

 

 

To confirm a couple of points: The aircraft was a Scheibe SF25 Falke (as opposed to a Slingsby T61A Falke – not that there is much significant difference). The aircraft was a later model with the swept back fin but was not the extended span Super Falke. I would almost automatically expect it to have been a C model, but once again there is little airframe difference between the B and C except engine size ie if you stood one of each side by side you cannot really tell them apart. The spoiler system on the B and C is identical.

 

 

The spoiler deployment data reported by L/D would therefore be valid for the aircraft that crashed.

 

 

If we put together L/D’s report and my own examination of the final flight path then we can firm-up some potential scenario a bit more.

 

 

It is positively known that the aircraft was in at least a 32 degree dive at the point of impact – that has been measured and in fact still can be measured very easily on the airfield. From the initiation of the yaw/side slip on approach to the point of impact approx 4 seconds would have elapsed.

 

 

From the Falke test pilot, as reported by L/D, the aircraft will, by itself and when not otherwise restrained , achieve a nose down pitch attitude of approx. 25 degrees and do so in 2 seconds.

 

 

The machine would have then covered half the distance between initiation of the yaw and the impact with 2 seconds of flight remaining. It would also have had to have achieved at least a further at least 7 degrees of nose down pitch in that time period.

 

 

None of the above is speculation and it may be proffered as virtual fact, but there are a couple of wrinkles.

 

 

None of the eyewitnesses could say if the spoilers were deployed at the point of impact or if they had been deployed at all.

 

 

This aircraft had all white wings with red tips but the spoilers were an individual colour and one that would merge with the nearly clear blue early morning sky. The spoiler colour may be seen on the general image of the aircraft given above.

 

Now, I need to say very clearly that it is not the prerogative of this Forum to allocate cause or blame. I have myself suggested to Ian that in fact this becomes a clearly stated protocol for this Forum. However, in the interests of education and self preservation of readers, it is practical to examine situations that COULD have resulted in what happened if there are facts to work with. From my viewpoint there are a number of scenarios.

 

 

• There was a significant failure, or blockage, of the elevator control circuit that caused and then left a residual nose down pitch condition. That can only be determined by the results of the airframe examination unless there was a blockage that dislodged at impact and so would be difficult to establish post impact.
   
   
  
• The aircraft was under continual, but gentle, forward pressure on the control column and the crew were obliged to let this situation continue whilst under the stimulation of considerable ‘ground rush’.
   
   
  
• The initial pitch down on spoiler deployment went unchecked and spoiler deployment was maintained stick free which would have caused a continual gentle pitch down until the aircraft stabilised aerodynamically. 200’ is insufficient height for a Falke to reach that condition.
   
   
  
• The aircraft was in some kind of stalled or post stalled condition.
   
   
  

 

 

On the latter point – I believe any kind of stalled condition is highly unlikely in the circumstances that were observed to obtain and from the normal behaviour of the Falke itself.

 

 

To obtain any significant nose drop at the stall in a Falke requires attitudes and activity that would have been readily seen from the ground yet the eyewitnesses saw nothing that suggested the aircraft was not on a normal approach.

 

 

If airspeed had been bled off unnoticed then indeed (in common with most types) the Falke will achieve considerable pre-stall descent rates. This would have caused it to belly in when in fact it dived in relatively steeply.

 

 

What actually happened is up to the investigation to determine. But I will repeat that I personally do not see any need for concern to anyone’s personal flying in Falkes if the aircraft is operated in accordance with the POH. There is simply nothing odd or difficult about the type.

 

 

Tony

 

 

[Guest TOSGcentral]

As a number of members have expressed appreciation of being able to obtain motor glider information in this thread – then for you power jocks out there who may want to sample a ride in a glider or motor glider, here is some more info about approach control systems that are (mainly) peculiar to gliders so you understand more about what the systems are.

 

 

In his post above L/D used the term ‘airbrakes’. This is a loose, almost generic, term to indicate the approach aids on any glider (other than tail braking parachutes or drag producing flap systems that are stand alone – eg Pik20 system or the more complicated rotating trailing edge/flap system on the Calif A21). There are in fact several different types of systems and each has its peculiarities. So I will go through them for those interested. Note: As in anything aviation there are always some weird and wonderful systems tried (eg the M100 and M200 gliders) but what follows is what you are most likely to come up against.

 

 

Firstly there are two main families of systems – spoilers (that are primarily lift dumping devices) and airbrakes that are drag producing devices.

 

 

Spoilers. These are flat plates, on the upper surface only of the wing, hinged at the front, and kept flush with the wing via powerful springs to prevent the wing’s reduced upper air pressure partially opening them at operating airspeeds.

 

 

They are normally positioned above the thickest part of the wing section so they have maximum effect on the wing lift. When deployed, and the lift is reduced, the aircraft goes out of normal stability balance and the nose automatically goes down to increase airspeed to match the reduced lift and restore the balance. Initially the nose down pitch is noticeable but will abate to a more gentle continuing nose down pitch until aerodynamic balance is reinstated.

 

 

In normal practice this is not allowed to happen and the attitude at approach airspeed is kept constant with the stick to counter the nose down pitch. The aircraft is therefore rotated to a higher angle of attack, balance is thus restored and the aircraft proceeds but now with a ‘dirty’ wing and sinking more rapidly. Variable degrees of spoiler opening may be used to give the descent rate desired to achieve the needed approach path.

 

 

Deployment of the spoilers is effected by pulling the control lever backwards (some systems have a toggle on the end of a cable in very early types) against the spring retaining pressure. Adjustment to spoiler deployment is effected by varying this pull force. Closing the spoilers simply requires relaxing the backward pressure (just letting go closes the spoilers with a bang and is frowned on by glider airworthiness bods!).

 

 

It is this system that the Falke had that figures in this thread.

 

 

Air Brake Systems. The most commonly found these days are the Schempp Hirth, DFS Top Paddle Only brakes and Rotating Trailing Edges. Each has similar purpose and actuation but different characteristics.

 

 

Basically airbrake systems are positioned as far aft in the wing as possible to reduce interference with the critical laminar flow for high performance gliding. The further aft they are then the less effective they become, so a compromise is usually struck – training machines tending to have them further forward than higher performance sailplanes.

 

 

There is normally no significant trim change with the systems and they are effectively just brakes – therefore a conscious effort must be made by the pilot to lower the nose and maintain airspeed one air brakes are deployed.

 

 

Schempp Hirth Airbrakes. This has two brake paddles in each wing, one above and one below and ganged together by rods so that they are interconnected and act uniformly.

 

 

They slide vertically out of the wing and at about half extension the paddle clears the wing and extends further, leaving a slotted effect under it. As both the upper and lower airflows are being equally effected there is normally no pitch change to the aircraft by deployment.

 

 

An important feature to this system is that there is normally air leakage through the wing between the two brake paddle openings, therefore airbrakes usually have a locking mechanism to keep them firmly closed. This is either parking the actuating lever into a side slot or, more commonly, an over top dead centre lock you release by a straight pull on the lever.

 

 

Because of the air leakage between high and low pressure below and above the wings, once airbrakes are unlocked the tendency is for them to open fully by themselves. This can be extremely powerful (particularly at higher airspeeds) and considerable forces may be experienced on the actuating lever (eg Ka7).

 

 

For deployment the actuating lever moves backwards. In practice this means an initial pull force to unlock and then a reducing push force to control the self-opening tendency. At higher airspeeds a considerable forward pressure may be required to reduce extension or close the brakes.

 

 

DFS. This also has a brake paddle above and below each wing. The design is quite different however from the S/H system given above. The two paddles are interconnected and lay flat with the wing surface. The top paddle rises and rotates forwards while the bottom paddle descends and rotates backwards.

 

 

As the two paddles are the same size there is aerodynamic balancing between them so actuating forces are extremely light. You can release the grip on the lever and the brakes will stay where set although this is not normal practice to do so.

 

 

The DFS system tends to be weaker in braking effect than the S/H system and requires more precision in approach skills. The most commonly met example is on the Blanik two seater.

 

 

Top Paddle Only. This is basically the top half only of the S/H system. The prime reason for the system is to entirely eliminate air leakage through the wing and the wing lower surface is entirely sealed.

 

 

The system is therefore much lighter to use than the full S/H system but correspondingly less effective in braking. Approaches are therefore flatter and require somewhat better judgement skills than the more powerful systems.

 

 

One wrinkle is that on extension up to the point the bottom of the brake paddle clears the wing the airbrake has the same characteristics as a spoiler. There is therefore a nose down pitch as there is no balancing effect from the missing lower paddle. This pitch down is very light and usually goes unnoticed – particularly as the system is confined to later generation gliders that have superbly designed aerodynamics.

 

 

Rotating Trailing Edge. With this system the airbrake occupies the trailing edge of the wing normally occupied by the flaps on, say, say a Cessna type aircraft.

 

 

A trailing edge portion of the wing has a spanwise central pivot bar that allows the airbrake to rotate. Once unlocked the forward edge rises and moves backwards while the trailing edge lowers and moves forwards. The system therefore has full aerodynamic balancing and actuating forces are extremely light.

 

 

The system is, surprisingly, not common although it is far the most effective braking system around. It is extremely powerful, light to use and leaves you with an entirely sealed wing over the critical laminar area.

 

 

Use of the Systems. Whatever the system is they are used in fundamentally the same way. My standard orientation to power pilots coming to the systems for the first time is as follows.

 

 

The main approach control visual reference remains the Aiming Point – as you are used to. The aircraft will be placed in an overshoot position although this may not be apparent because of the high glide capability. In the case of a motor glider the throttle will now be fully closed. You will now use the airbrake lever exactly the same as you do a throttle to control the approach.

 

 

A caution is given on a spoiler system that the nose must not be allowed to drop during deployment and that on an airbrake system the nose has to be deliberately lowered to maintain speed. A final safety point is leave the brakes at the current setting when within one wing span of the ground (in the early days of training) unless reducing them to abate high sink but do NOT extend them further!

 

 

A couple of minutes upper air exposure to how the system feels and I have never had a problem. Enjoy!

 

 

[Tony]

Rudder pedal return spring

 

To TOSGcentral,

 

Q: Does Falke has got Rudder Pedal Return Spring system ?

 

If yes what is the exact arrangement.

 

Thanks in advance if you don't mind to tell me about it.

 

Tony Milan

 

 

[Guest TOSGcentral]

Hi Tony,

 

No probs mate.

 

The Falke rudder assembly is basically 'open circuit' unllike, say, an elevator circuit that is tensioned and locked tight by turnbuckles or push rods and their adjusters.

 

This is common to most gliders, motor gliders and indeed most very light aircraft. It is a light and effective system.

 

This "open" system has restraining springs or bungeys to keep the pedals upright.

 

It's main purpose is to stop the pedals flopping forward and laying on the cockpit floor which is difficult to get at them. Main rudder circuit direct drive is therefore actioned by foot pressure, so it does not really matter if the springs are there or not once you have your feet on them.

 

To not anticipate where you may be going but to add further insight - the Falke rudder pedals are very heavy. The aircraft does not suffer from rudder overbalance and may therefore stay locked in a slip or yaw configuration.

 

Any relaxation of foot pressure on those pedals would have seen automatic stability take the aircraft out of the yawed state that it was most clearly in at inpact.

 

I am prepared to take further questions on this - not on what happened, but surrounding factors that may give us generic insight to this form of accident.

 

Aye

 

Tony

 

 

[Tony]

Hi Tony Hayes,

 

Away from Falke to Thruster I am learning to fly. Some Thrusters and other RA planes do have two separate pedal return springs/rubberbands to tension the cables.

 

Some don't.

 

Each rubberband represents a pressure on the pedal of approx. two kilos by my estimation.

 

Should one rubberband fail, the remaining force of the other rubberband will push down the pedal to which it is connected - at the force of two kilos.

 

I would have to rather quickly balance that by pushing the other pedal at an equal force.

 

The third tiny 'trimming' rubberband would not help me.

 

Further, if I am unlucky enough to loose/snap say left rudder link cable in this arrangement my rudder would be instantly in full right, so I must be prepared to lift(!) the right pedal at once to sustain the straight path somehow, otherwise.....

 

Does a Cessna or Falke have some better arrangement with return/tension springs in the rudder assembly, so the above cannot happen ?

 

Thanks, Tony Milan

 

 

[Guest TOSGcentral]

Hmmm! I see the point that you are driving at Tony but your concerns are not of consequence to reality.

 

As said, the springs/bungeys are just there to give some tension to the rudder circuit when your feet are not on the pedals.

 

One or either of those tensioning devices could break in flight and you would not even notice - unless you are in the habit of removing your feet from the pedals.

 

That could happen in a two seater with dual side by side controls but just the weight of the other pilot's feet would totally over-ride any effects even without any force being applied.

 

You also have to consider airflow forces on the control surface. At the worst you may feel slightly out of trim in yaw but little else - no great forces would be at work that would take control from you.

 

There is the possibility that some clown may have put in really heavy springs but I cannot comment on hyperthetical illegal modifications as they could be anything.

 

Tony

 

 

[Tony]

Hi Tony Hayes,

 

Let me confess. In my early stages of learning Thruster I was the white knuckle guy. Those days are over. I can fly Thruster for 25 minutes without touching the stick on vertical trim, or without my feet on the rudders, thus using the stick in two fingers instead - providing I have the power right. And, I have a lot of to learn ahead....

 

I used to push the stick 'down' (not forward, back, left or right) as far as it would go like an idiot, stay on both pedals as hard as I thought it is a comfortable grip for me, paddle them like mad cyclist and bracing my right leg against the central panel so hard I had scars there for the rest of the each day.

 

Now, I can feel my instructor has his feet rested on his pedals or not. If I pressurize one pedal at the force of any rubberband my flying instructor would tell me to "get off the pedals Tony", if it was his plane at the moment. And vice versa, I would ask my instructor if he has his feet on it, because I can feel something. His answer is usually "No Tony". So I put it to the wind. Normally, we do not have four feet on it.

 

If there are two really too strong springs used on a Thruster and if one goes (not both) I believe it can create a loss of lateral balance which must be addressed by the PIC. I have seen double steel springs used on RA pedals so strong as it would keep a paddock gate closed.....

 

If they are not that too strong the same snap off scenario would only rise a question what is going on to keep the PIC busy a 'little' bit more, there it is I would agree with your benign mechanics.

 

Tony Milan

 

 

[Guest TOSGcentral]

To extract another safety point out of Tony’s comments above:

 

 

The legs have the largest and most powerful muscles in the body. While their prime function is to allow us to stand, walk and run – far more applied power may be extracted from them when not performing any of those tasks, eg when sitting.

 

 

When you are seated in an aircraft with your pelvic girdle firmly strapped to a seat back to provide reactive force – a massive amount of power may be generated by the legs in terms of forces required on the rudder pedals. That is of course if you are seated correctly.

 

 

To access this muscle power your leg must still be slightly flexed when extended to the full travel of the rudder pedal. You in fact actually operate the rudder with knee action rather than foot action.

 

 

If you go to full leg extension then you become involved with the geometric lock mechanism of the knee. This is an ‘over centre’ affair that allows us to stand for long periods without a great deal of muscle use.

 

 

At the point of going over centre at the knee joint, your leg muscles are virtually useless in terms of power and you become dependent on your feet and ankles for the rudder pedals. This is tiring, uncomfortable and you do not have as much control as you otherwise may. So in itself this becomes a safety factor.

 

 

One of the first things I taught students was how to correctly seat themselves and strap in to the aircraft – using seat adjusters or cushions if necessary. The determining factor is to apply full rudder in both directions and ensure that you still have at least some bend left at the knee when at full travel of the pedals.

 

 

I then insisted that they remember this position and never be stampeded into flying until they had initially obtained the correct seating otherwise the aircraft may ‘feel’ different and their control of it would be less than it may be.