fire / safety discussion threads

[t-bird]

Deleted

[nicow]

That's a good thing to install-it can safe your life.

[Learjet]

Thanks T-bird - given the various discussions which have started on other threads about fire safety etc - let's use this thread started by T-Bird to discuss fire extinguishers, deto-stop, safety-wear & flightsuits etc which can all help contribute to fire safety and awareness.

[Gyronaut]

I have been informed the following by the Magni Agent, Butch Brown:

The fuel tanks on all Magni gyros comply with British Civil Aviation Regulations Section T requirements and are fully tested to withstand loads of:

9 g forward
4.5 g vertical
3.0 g sideward

As I understand it this test is done with a 90kg weight simulating a passenger on top as the Magni has an integrated back seat tank on M16's and M22's and both seats on M24's.

Crucial to have metal airline type seatbelt fasteners. I know of two incidents now where the plastic ones would not release resulting in severe burns to the occupants.

[OzGyro]

Hi All

There was a lot of discussion on this topic back home a few years back as a result of a fatality and very serious injuries associated with the same accident. In my time in the gyro world and from the reading I have done, the accidents I have witnessed one common link that seems to have occured in the majority of the accidents. Gyros with high pressure fuel pumps the likelihood of fire seems to be greatly increased, as we all know fuel does not burn as a liquid but as a vapour. In many of the accidents I know of the fuel tank/cell itself has remained intact the problem seems to be when the fuel lines are torn or dislodge from the motor itself and the pumps remain running at high pressure, the atomised fuel that is spraying around then contacts the engine/exhaust etc, in most cases the enevitable fire has ensued. I have witnessed a serious accident in a machine with a mechanical pump which tore the lines from the engine and fuel was pouring from the tank and no fire occured, I know of and have witnessed several other accidents in fixed wing, trikes and gyros all that had mechanical pumps and none of them resulted in a fire. I am not saying it dosn't happen but the incidences of it just appears less frequent.
How do we rectify the problem, there is no ultimate solution apart from giving up flying and we all know that is not going to happen. I have worked in the industrial industry for almost 25 years and there are two sectors that already utilise systems that could be incorperated into gyros with minimal expense.

The first is a safety lanyard system like that that is used in the boating industry and for jet skis, the safety system is placed into the fuel pump circuit and in the event of an accidient the lanyard is torn out and the fuel pumps will shut off. For those who are worried about accidental removal inflight a bypass/backup up switch can also be utilised allowing you to manually repower the pumps inflight.

Secondly is a pressure switch (Hobbs/Murphy) like they use in the racing car and heavy industrial industries. A pressure switch is incorperated once again into the fuel pump system, however this switch relies on oil pressure from the motor to keep it operating. A overide is fitted into the system that has to be operated on star up, you simply depress a overide button on initial start up and once the oil pressure of the engine closes the contacts it keeps running. So basically it means in the case of an accident and the engine stops running the oil pressure is no longer present and the fuel pumps no longer operate.

I know this will definately not stop all fires, however the whole idea behind this is safety and risk minimisation. The real problem will lye in getting it implemented into the real world. Lets hope that people far more knowledgeable and influential than I give it some serious thought, I would hate to think it will take another serious accident or even worse a fatality or two before we can overcome the red tape and beauracracy and make it happen.
Just my thoughts

Cheers and safe flying to all.
Darren

[fransstrydom]

Darren,i like your way of thinking.Every possible means to minimise the chance of a fire should be investigated.The problem with burning is that it not only scars you on the outside.Emotionally it take years to recover from burning.Already on this forum a couple of good practical suggestions came forward.A fire extinguisher like we are forced to carry onboard now is of little help in a situation like we had.
Scary Pilot
Proud Sycamore Owner
ZU-CCN
RHINO PARK

[ZULU1]

Darren, then the answer would be a normally open by pass valve back to tank after the two high pressure pumps, use stainless braided tubing for all fuel lines. When power is applied to the network, the normally open valve closes and when its switched off the fuel pressure in the network returns to tank. That would leave zero fuel pressure between the carbs and the fuel pumps. The technology is available freely as its used in gas powered fork lift trucks. Basically a change over as they start on petrol and switch to lpg when running. BF Goodrich make the fuel lines, best load the gyro on a trailer and take to a hydraulic specialist. I did that with oil hoses. The oil powered device would operate in the same way.

[Gompou]

Hi Daren and Paul
I am in the proses of rebuilding a giro, so find this topic very relevant.
The stainless braided tubing make very much sense and would be much more difficult to rapture or brake in a case of an accident.
My problem with the oil pressure switch is that in a case were you get a loss of oil pressure, or very low pressure, or an engine out for any reason, your fuel line will be cut. In a emergency situation, you now have to remember the bypass switch as well for a attempt to restart.

With the bypass valve, you will need a alternative power source like the power from the alternator to keep the valve open. No use to put it on a switch from the battery, because then you can switch of the fuel pumps in a case of a accident also.

Now I know that people like Paul and other electronic minded people must have the know how to take something like a automotive airbag sensor ( read impact sensor) and then connect it to the fuel pump power line . This will then in a case of an accident\impact, switch of the fuel pumps.

Please feel free to comment on this please. As I said earlier, I think this is very relevant and with all the knowledge on this forum, it must be possible to design something simple that can be of use to the whole microlight community. I also fly a trike, and although it make use of a mechanically fuel pump, many triker's put in a electric pump for backup for take off and landings. In a case of a accident while this pump is on, the scenario is much the same as with a giro, and the fuel pump will probably keep pumping until the power source is remove.

Fly safe
Gompou

[ZULU1]

Gompou, I have been thinking about this as well, I dont like electronics for the sake of their usage. Darrens post pretty much summarizes the problem and how do we fix it ?

On impact the fuel lines rupture and the pressure between the carbs and the pumps will spray the motor and that is the source of ignition..thats the main issue it seems.

Problems to solve:

1/ Obviously braided fuel lines would be an immediate short term "Must have".

2/ How do you release the pressure in the fuel system (between carbs and pumps) when an emergency.

Now if a solenoid valve/oil pressure relief as suggested, this will cause an engine failure if it gives a fault, not ideal but it will work. The solenoid must be 100% duty cycle. Now in hydraulics they use pressure relief valves that can still by pass and signal at different pressures and so on, not going into detail but I know the subject fairly well as having designed kit years ago. Maybe the area that we should be looking is a by pass thats pressure related but also fail safe in flight. Not so easy but this thread serves to find the solution.

Maybe move the fuel pumps closer to the carbs to reduce fuel in that section of line.
An Emergency stop button as used in machine tools would work with a solenoid, maybe a bowden cable operated valve would work in a similar panel mounted scenario.

Keep thinking...

I had a similar wiring problem with a HKS motor as they stop if they dont power themselves.

[ger koff]

Hi all

As far as I know all modern cars address this issue in the following manner.
When the ignition switch is switched to the "on" position the high pressure fuel pump switches on for a fixed amount of time (about 5 seconds) and then switches off. The driver then starts the car and the engine ECU (engine control unit)receives a signal (from the crank angle sensor)indicating that the engine is rotating. The ECU then allows the fuel pump to continue pumping fuel. If, in the event of an accident the fuel lines are ruptured the pump will stop pumping (assuming the engine stops running). This method seems to work in most car accidents but could probably be improved upon with the addition of an impact sensor.

[t-bird]

Hi Ger koff

The 914 uses two electric fuel pumps.
They will keep pumping as long as they have power.

[Gompou]

Hi Ger Koff
Thanks for the info. Would that mean if you use a Toyota\Subaru engine with a aftermarket ECU that you could program it in the same way?
The problem as indicated by previous post is not the pumps that keep on to work after impact, but the fuel that is still in the pipe between the carb\injectors. This is under pressure and when rapture, become a vapor and is this much more flammable.
Perhaps a NC solenoid connected to a impact sensor can relieve this pressure quick enough?
It can in the same time stop the pumps from working.

Just out of curiosity, does the 912 Rotax use both fuel pumps all the time, or do you select pump 1 or 2 ?

Gompou

[Hub-Bar]

This discussion is really starting to bear the fruit that will make a difference in the future. Apart from changing things mechanically, it is vital to kill the fuel pumps before an impact. We are all trained in the mantra of ‘fuel pumps off - electrics off’ in an emergency landing scenario. If you have an engine out, even low as T-Bird has demonstrated, this training kicks in and you can manage. If however you find yourself in a behind the power curve or downwind dragon situation, the throttle is wide open, turbos are engaged and you are instinctively going to try to fight your way out, right up to the point of possible impact. There is probably no way in these situations that you are going to willingly close the throttle before impact. Here we have a lack of precisely defined decision point before the impact (as in a definite engine out), leaving you with zero time to act. While all this is going on (seconds) your left hand is probably glued to the throttle which means that it is actually not contributing anything to the situation. I suggest that we incorporate into our training programs a drill which dictates that when encountering ‘perceived power loss’ situations close to terra firma to immediately take your left hand off the already fully open throttle and place it on the master/ignition switch ready to switch it off just before unavoidable impact. The position of the master/ignition switch is going to play a role. You are totally balanced with your left hand on the throttle and right hand on the stick. If you have to reach say to the right for placement of your hand on the switch it might leave you in an unbalanced position which could psychologically deter you from doing it – therefore it must be practiced regularly. An even better option would be to incorporate a kill switch in the throttle mechanism by means of a gate or resistive rear position which means that if you forcefully close the throttle past the gate or resistive normal stop, a switch will engage (or disengage) and switch off all electrics. A good idea would be for this throttle kill switch to act on dual redundant relays right at the battery – thus severing electrical power to all wires leading into the aircraft. (Don’t know if this can be done practically with the starter motor cable though.) This rearward kill switch position of the throttle can also be utilised to mechanically actuate a cutoff valve in the fuel line right at the tank (also a mechanical pressure release valve for the pressurised part of the fuel line for that matter.) Lets talk about this – give some input.

Francois Marais (Gansbaai)

[t-bird]

Hi Francois

I have to agree that it would not be easy to switch of the mags and master when trying to recover after flying behind the curve.

I have witnessed a gyro getting behind the curve and the pilot was applying full power and could not recover but landed very hard.
The engine backfired when he hit the ground and you could see a flame of about 15 cm in daylight coming out of the exhaust.

[ZULU1]

I have been thinking about a master kill switch and as I am not a gyro pilot don't really understand the detail of flight control so forgive me if I am not contributing correctly!

If a device such as a standard 22 mm latching type emergency stop switch was installed, this could be configured with many sets of contacts. 1 for each fuel pump, 2 sets for n/o petrol return valves, a set to drill the mags and a set to disconnect a main power contractor. The common telemechanique type are freely available.