Is static line really needed on an altimeter in a rag and tube plane?

[danny_galaga]

If I don't that's one less thing to go wrong and a few hundred grams of tubing less tubing to install.

[kasper]

Depends on where the instrument is and how impacted the air around the instrument is.

 

If your alt and asi are in an environment where ambient pressure is pretty stable and unchanged due to the airframe from true local static then don’t bother and just be aware you have two holes in inaccessible locations that may be subject to mud wasp blockage.

 

If the local air around the instruments is variable due to speed and/or different t from ambient local then you need a static port. Eg inside and open cone the pressure drops with airspeed ... a nosecone/pod may do this but at the speed of rag and tube prob not an issue.

[Bruce Tuncks]

Worth a try in my opinion. There is a standard glider training session where the student has to fly with the altimeter and the asi covered up. Most students flew a bit faster than normal and maybe started the circuit a bit higher. You are contemplating much less than having no altimeter at all. This check was done because a glider may land at a place with unknown elevation.

I dunno the argument behind the asi covering. But I reckon a good pilot shouldn't need an asi.

You could investigate in the air if the indicated altitude varied with speed or not. It would with a fast and slippery plane.

[danny_galaga]

So just to be clear it will be in my Bushcat. So in a cabin, but not one that could ever be considered airtight

[kasper]

Ok. The bushcat is just a variation/development on the theme of the original rainbow aircraft line.

 

One branch on that line is the Medway SLA and Executuve aircraft that are type approved factory aircraft in the Uk and I know them well. Static to cabin in those aircraft made no measurable difference over full static port setup.

 

I’d go with open port and see how it goes.

[spacesailor]

Stick a filter over the end, something like a microphone cover just to safeguard the instrument from insects.

spacesailor

[danny_galaga]

Stick a filter over the end, something like a microphone cover just to safeguard the instrument from insects.

spacesailor

 

Yep had already envisaged doing something along those lines. Hadn't thought of a microphone filter though. Genius!

[danny_galaga]

What I'll finish cable tie the cover to a short length of PVC tubing with a few small holes burnt into it. Just to keep the foam away if it crumbles over time

[WayneL]

Had an aircraft that had a cintered brass filter in a short static port tube behind the dash. Worked fine.

Wayne

[danny_galaga]

Had an aircraft that had a cintered brass filter in a short static port tube behind the dash. Worked fine.

Wayne

 

Just bought a cheap little sintered bronze filter with a 1/4" fitting that seems to be designed to give just the right 'fffffftttt' in those turbo ricers that bogans drive ?

[M61A1]

Just bought a cheap little sintered bronze filter with a 1/4" fitting that seems to be designed to give just the right 'fffffftttt' in those turbo ricers that bogans drive ?

The sintered bronze thingys are mufflers for pneumatic valves. They seem to start at 1/4 BSPT. One could probably get an adaptor,, but all you need really is a plastic bung with a very small hole in it.

 

As far as "needing" a proper static setup, it will just depend on how accurate you want things. The ASI, ALT and VSI in my Drifter used to do silly things at high AoA due to the low pressure formed behind the pod. For example the VSI showed a fantastic rate of climb for a bit when you added full power and put the nose right up.....then you realise it's lying.

The difference between real static and cockpit static in the 601 is about 20 kts worth and doesn't change much with both vents (NACA ducts each side of the cockpit) wide open.

[danny_galaga]

Nuts, are you saying that is bigger than the 1/4" that my ruler says? I was goi g to get a sintered filter for an RC Cl no tank but they are 3.5mm and u couldn't be arsed making it fit ?. Maybe I'll just cable tie a piece of stocking over the tube...

[spacesailor]

It,l stop those creatures giving you hell !.

spacesailor

[M61A1]

Nuts, are you saying that is bigger than the 1/4" that my ruler says? I was goi g to get a sintered filter for an RC Cl no tank but they are 3.5mm and u couldn't be arsed making it fit ?. Maybe I'll just cable tie a piece of stocking over the tube...

Normally the instrument fittings are 1/8 but 1/4 bspt is the size nitto air fittings are, not 1/4" actual dimension.

just use a 1/8 BSP plug and drill a really small hole in it. also acts a a damper then.

[Jabiru7252]

Worth a try in my opinion. There is a standard glider training session where the student has to fly with the altimeter and the asi covered up. Most students flew a bit faster than normal and maybe started the circuit a bit higher. You are contemplating much less than having no altimeter at all. This check was done because a glider may land at a place with unknown elevation.

I dunno the argument behind the asi covering. But I reckon a good pilot shouldn't need an asi.

You could investigate in the air if the indicated altitude varied with speed or not. It would with a fast and slippery plane.

 

When I was learning to fly back in the early eighties, my instructor (upon arriving in the circuit) covered the panel and said "You can fly the circuit on sound and attitude". He kept saying that if I kept the horizon in the correct place on the wind-screen and the throttle about right then speed and descent would follow. If I kept the runway in the right place then I'd land okay. He was right but boy oh boy, I don't think I could do it these days. He could see the instruments and did mention that I was faster than normal until crossing the fence then got a bit slow.

[M61A1]

I don't think I could do it these days.

If you fly the same aircraft regularly, I doubt it would be a problem. It's not just sound and attitude, it's feel as well. My partner that flies with me knows when I'm doing stuff out of the ordinary by the way it feels.

[Yenn]

I have found that a piece of fine wire in the inlet to static and fuel vents stops insects. They will not build a mud nest in the opening. I did get insects in the static before I used the fine wire and it was only a pop rivet with the stem knocked out. The wire I use is stainless lockwire.

[danny_galaga]

Was thinking of a bit of wire earlier. Good point on the fuel vent too. Totally forgot about that!

[facthunter]

Use fine wire mesh in brass or buy a lawn mower fuel tap filter. Most cabins run a below ambient pressure which gets more so as you go faster. In an 8o k cruise plane you probably get away with an internal vent. It's the fail/default position for the flush vent which is usually duplicated on both sides and interconnected. Nev

[Thruster88]

Most of the Thrusters I have seen have had the external static probe removed. This make the ASI read about 10% high. My advice regardless of the type of aircraft you fly, certified or amateur built is to regularly check the indicated stall speed for different configurations and weight. Know your aircraft. Stalling is fun when done intentionally.

[facthunter]

Most pilots I've flown with are $#1t scared of stalls. That's not a bad idea if you can't handle them and in those circumstances don't do them. In the absence of an angle of attack measuring instrument a good feel for the approaching stall is required. IF you are likely to do or have done an inadvertent stall get more targeted intensive instruction in stalling theory and practice.. Carrying an adequate stall margin is the usual way but a gust can dispense with that on occasions and you should be able to cope with that. Nev

[Blueadventures]

If I don't that's one less thing to go wrong and a few hundred grams of tubing less tubing to install.

My understanding of things is that you only place the manufactures designed or described static ports were they say. This is because as I have been told is that the positioning needs to be calculated and tested as the aircraft profile will cause high and low pressure areas in locations on the fuselage and also the profile of the actual static ports themselves can cause the same high or low pressures due to their shape / profile ( raised , flat, etc) and the air flow over them.

 

In my Nynja they say have vented behind instrument panel. I have done this and placed a plastic plug in the end of the tube with a small hole in it.

 

Best check if the 'Bushcat' people state a design and position, if not perhaps check ASI on its first flight by getting up high above the airstrip, say 4,000ft and bring her back to the stall and check the reading (this will be part of the test schedule). The ports either side mostly balance the pressure of each side so you have neutral pressure affecting the instruments connected.

 

Cheers. Post some images of where your at with the build when you can. Cheers

 

I finished off a build and checks for mate the other day and had some fun doing some strip runs and the sun was almost down; for him. Video too big but here's our smiles after, nice to get a beer when all packed away.

[danny_galaga]

Use fine wire mesh in brass or buy a lawn mower fuel tap filter.

 

You're a genius! Spot the difference ?

[M61A1]

You're a genius! Spot the difference ?

Perfect...

[Bubbleboy]

I have recently got my Cheetah-XLS which is the BushCats older brother flying. I have a steam gauge ASI and a MGL panel and no Static line per say. It just vents in to the cabin. Both read within a very close tolerance. I wouldnt worry about it.