Geoff_H

Many years ago a Chipmunk VH FTA spun to the ground and killed both on board. Not long after an experimental made of Kevlar also spun into the ground. The pilot got out and walked away. The Kevlar all stretched and destroyed but the energy was absorbed by the Kevlar. When I trimmed Kevlar on a layup the Stanley knife had chips in the blade from cutting it. Very tough stuff that.

Is this failure of the window struts common? It seems like the floor is absorbing most of the impact. But the doors are not sticking closed and locking the pilot and passenger in. Must be good if a fire develops. I still would be somewhat worried at such a significant structure failure in an accident, but it seems to work for the better. Amazing! It just shows how not everything is as we would imagine.

I think that I would rather have my cabin remain enclosed. It broke at the highest loaded parts, the side window struts. I am glad all survived.

I must disagree that structure strength is more important than energy absorption of the structure upon impact. A totally rigid structure will not impart an infinite force that will break the structure. Impact absorption is more important as this reduces the energy available to cause very high stresses that will break the structure. The triangular steel frames work by the high impact absorption on deformation of the steel. The real performance indicator of a good design in a crash is the energy to deformation and in an aircraft the weight must also be a parameter. When considering theses parameters carbon fibre with Kevlar wins. Triangular steel frame design is in the same class but heavier.

If you are looking at composite aircraft and are serious about the amount of energy that your frame will absorb before you start absorbing the energy, (not so good), but want a strong light structure you would use an interwoven carbon fibre and Kevlar cloth. It costs around five to ten times that of straight glass but in Izod impact tests absorbs over twice the energy of straight glass. You will be paying for increased crash absorption. How many of us would pay for that option?

The Mooney cabin is a safety cage design

Some of the very early experimental aircraft used Kevlar in their construction. A flat spin with the pilot walking away was regarded as fantastic safety. Problem is that it is tough not strong. Some cloths use carbon fibre and Kevlar interwoven to give strength and toughness. I designed and started to build a glass aircraft with a layer of Kevlar. It was far too heavy and I abandoned the project at fuselage stage.

Have a look at the amazing survival rate of the Mooney. Tail is monocoque but cabin is steel frame with aluminium covering. This is design for minimum weight and maximum survival.

The ones that I used required heaters to keep the element at a constant temperature, around 1600deg if my memory serves me right. I agree that one for each combustion chamber would be needed to get an accurate engine situation. I don't know what the IC injection systems use. The early ones were not nearly as reliable as the later ones.

Yes. I have used them extensively for oxygen trimming controls in exhaust gas systems. They need constant recalibration, so nitrogen and part oxygen gases to frequently calibrate. The best systems automatically calibrate. I am not sure that they would be suited to aircraft, but I think that many vehicles use them.

For me parking outside was the same cost as hangaring. Hangar fees use maintenance costs added together seemed to remain constant. Maintenance costs went very high when no hangar.

In the 80's I owned a Piper Cherokee. I hired it out. Continually dirty. Watched as one pilot continued to attempt to start engine with loud grinding noise coming from engine. Did damage to starting system that would have been far less than if he had aborted the flight. Never rented my Mooney. Most guys I know that have rented aircraft to help pay for ownership end up just selling the aircraft. I considered renting the Mooney by putting it online with a flying club. The terms that they wanted were so one sided. So I sold the aircraft rather than not use it when the wife refused to leave the ground!!!!

Use only Tefzel wiring. It is similar to Teflon but I'd less toxic when it burns. PVC wiring is much heavier as the insulation needs to be much thicker for the same wire cross section. A cables ability to carry current is a function of the temperature that the insulation can stand and still be functional. Teflon and Tefzel can take higher temperatures than PVC. A thinner wire will get hotter than the same current through a thicker wire, so a thinner wire will get hotter but the Tefzel can take the increased temperature. Lighter copper and insulation, good for aircraft

Don't solder connections in any vibrating machine. It will cause wire fatigue breaks at the solder/ wire interface. Use professional crimping with PROFESSIONAL crimping tools, this ensuring a galvanic connection.

Have two distinct electrical systems. One for power the other instruments and radios. Each should have an earth bar. Connect each earth bar by one only connection. Do this and you will reduce problems with earth loops that an affect instruments and radios. Shield all instrument and radio connections earthing the shield at one end only, very important to also stop earth loops.

I read an article once where the ashes a guy distributed from his aircraft ran along the skin of the aircraft on release and damaged the aircraft paint work. Apparently they are very abrasive.

Yes all the Teflon style of wiring is hard to skin, even with a skinning tool. In the 70's we used lots of Teflon wire for control cabling in very large control installations. Packaging density very high but the gas given off is really bad. When Torrens Island power station had a fire in their computer control room the fumes subtly destroyed most control cards in the system. The insurance company paid out for a complete refit control system. Hans I would replace all wiring in an aircaft if I ever had a small fire anywhere in that aircraft.

Actually aircraft wiring is not Teflon, similar in properties but with less toxicity when burning.

The downward force that the aircraft exerts on the air supporting it will increase! Then as time progresses the aircraft will get lighter! To raise the potential energy of the birds (increased height above the earth) the birds must exert a force on the floor of the aircraft. This requires a thrust downward from the wings of the birds. The birds will increase the altitude of the centre of gravity of the craft. This has the effectiveness of pushing the aircraft downward, the velocity of the downward force will increase its force under the wings of the craft. When the birds reach a constant altitude they will no longer exert this force and the aircraft thrust downward will return to its previous bird seated value,....... Well not exactly! The birds will have expended heat in the process of raising their potential energy. This heat will have come from chemical energy, so they will be slightly lighter this reducing the weight of the aircraft. Ever so small changes, but no one said anything about not being precise lol

Ian, how do I start a blog of my aircraft build? Is that ok with you?

I am a habitual user of this site. Can I get notified on my android of new posts? I would like to see blogs of what people are doing! Be it Recreational aircraft, GA Aircraft, regular public transport, model in fact anything that is above ground and uses air to support it, even hovercraft. All can be recreation of some sort. I would also love to see pics of cars being restored, maybe not aircraft but still of interest. I have not blogged my aircraft, I will, but I get all sorts of agro from she who must be obeyed.

I left Facebook after criticism from my left wing family of my right wing views. Total intolerance and criticism. Why be criticized. I look to this site to exchange information about mother nature and our battle with her to fly. I need to build cowlings, the thread was just what I wanted. But I am not good with writing, a little Asperger's, I got lost in the words. I am guessing many of the people interested in this website maybe similar to me. I would like to see pictures of some of the ideas and methods. Open discussion on all aspects of aircraft big and tiny. Of all types of ways of doing things. An open forum to exchange ideas freely and without fear of being criticized for anything. I think that the ability to ask a How do I question would attract persons like myself. There seems to be a lot of us if the what else do you do thread is any indication. When I do a google search on an aircraft technical issue I find it surprising how many times I get refered to this site of some years ago.

Many years ago I read a report from a retiring six crash investigator. He said: 95% of accidents involving death the pilot was doing something illegal at the time of the accident 1% was bad pilot training 1% was bad maintenance 1% was pilot medical episode 1% was something I can not remember, old age memory. 1% was bloody bad luck So I used this as my philosophy, fly legal, it is legal for a reason. Seen me safe for 40 years of flying. Still have a class2 med. Reaction time is still in the .3 seconds. If this goes I will retire from flying.