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Wright Air Service STC (Injection System)

Started by Neil, January 01, 2021, 08:37:28 PM

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Hello everyone
Louis and I, We just finished 20 hours flight with the new  STC I just installed, the STC consist to  modify from Pressured Carburator to Bendix RSA-5 Fuel injection System from Wright Air Service, I made this modification on the Louis’ H295 C-GZZL, this injection system is very similar on the most common Lycoming IO-540 and IO-360, and it is not a complicated job for modifying the airplane. The STC stands out the day you start the engine, a smoothness that I have never achieved with the carburetor. With the Carburetor the CHT and the EGT on each cylinder is never equal on any stage of power. Especially in cool winter with the carburetor at take off power, the carburetor was not sending enough gasoline and the engine was not reaching a smooth at max power and I had noticed as much on C-GZZL as C-GBYA. Now same engine with the injection system, WOW!!! soft at all RPM with the EGT and CHT which goes up and down all equal as I saw in several plane with Lycoming IO engine. The manual control of the mixture is unequivocally much more precise than the automatic carburetor. This STC is perfect



Interesting...what was the total cost if you don't mind saying?


Cost will depend on a couple of things.  It is mainly time consuming.  But as Neil said, the work is very straightforward.  Nothing had to be invented ( is it a good word in English ? ).  The plans and parts were taken from Lycoming.  Lycoming did design a 480 with injection.  They might not have produced any, but the plans and engineering was available.  All with their standard fuel injection parts.  So that makes it difficult to give a cost since these parts are available used or new.   Old cylinders already had the threaded hole for the fuel injectors.  Wright STC gives a method to make that hole if your cylinders don't have them. With some kind of homemade jig.   So you can use your present cylinders.  They are all cast by Lycoming with the necessary metal and shape to accommodate the injector hole as per the STC.  So this is time consuming again.  You probably have to remove them from the engine to machine the injector.  Neil would know if you can make that without removing them.  Installing the injection spider on the engine is all standard Lycoming parts.  There is one or two instruments that have to be added in the dash if you don't have them or equivalent.  I think we already had them.  One is a fuel flow, the other one i forgot.  Neil will tell.  Probably a fuel pressure gauge.  Maybe the electric pump has to be set to a different higher pressure  ( from 22 to 27 ?  ).  But it is the same model, just a pressure different setting.  I write those things even if i am not sure so Neil can correct me and that he won't forget to talk about those. 

Wright was able to have that STC for a good reason:  the installation was from Lycoming plans.  And they had thousands and thousands of logged flight hours with a couple of machines since a long time with that installation on 337 one time approval forms.  Applying for an STC was a no brainer. 

Neil did mention the way it works better at low altitude fuel power.  At minus 30, the standard carburetor was way too lean.  It could not adjust to a minus 1000 feet pressure altitude.  So often we would have to put the carb heat for take off for a smoother run   ( more percentage of fuel for the air since the carbheat air is less dense ) .  That would put the mixture more rich by providing a higher altitude pressure.  One that could be enriched enough by the carb.  But there is also a big difference on the other end of the spectrum.  We were able to go to more than eleven thousand feet by leaning so each cylinder would receive just the right amount of fuel for the mixture. 

For fun, we did put Gami injectors and control them as per instruction of Gami to have a perfect fuel flow for each cylinder peaking them at the same total fuel flow.

So cost is difficult to pinpoint, since Neil did a lot of hours to install all that perfectly.  And more hours to play with it.  Neil could probably tell us how many hours he thinks the installation can take.  But you also have to put the time to find the parts.  Let's say it is something that you do if you have free time and resources.  Maybe at the time of an engine overhaul.  Or when your pressure carburetor has to be changed.  For the ones that have the time and resources to do it, go for it, you won't regret it.  There is zero wrong side for it.



For the cost Louis is right depends on the condition of the parts. New, Use, Overhaul, Serviceable, Exchange. This is the list of the major parts you need: Google the number for the cost
(1) Fuel Manifold 2524232-2
(1) Fuel Servo 2524634-8
(1) Driven Fuel Pump RG8090F2 24 Psi
(1) Electric Boost Pump for injection engine 4140-00-17N
(6) Nozzle LW-18265 or 2424864-2
(6) line LW-12098-xxx
(1) Fuel pressure gauge 5200-01
(1) Manifold press/fuel flow gauge 6331

For the GAMI, I make few hour before with the Original Lycoming Nozzle, is perfect. My goal with the GAMI is not to going lean of peak, is to maximize EGT and CHT as equal as possible, yes, I had an improvement but from a situation which was already perfect.

For the hole you need in the intake cylinder port, some old cylinder series have this hole from Lycoming, me I make jig with use IO540 cylinder (same valve cover as GO480, the triangle angle valve engine valve cover), to find the angle and the place to drill the hole, but Wright Air Service sell this tool. I make this job on the cylinder on the plane with great care, with the intake tube removed, intake valve closed and a good vacuum cleaner nearby.
For working time it’s difficult, I have perfect big hangar with all you need, a good week on the airplane plus paper work and parts search

I thank Wright Air Service for bringing to life an idea that was on the shelf at Lycoming and for passing the process an STC. Bravo



Neil just showed me the instruction from Wright to do the project.  It is perfect.  Very well explained.  All the process one by one with color photos.  Even me i was able to understand most of it.  Really a fun project with low chance of something wrong happening.


Doug Johnson

 I believe Wight air deserve the credit for putting a working fuel injection system on the Helio and developing the STC but....

I'm pretty sure the first IGO-480-A1B6 was Helio c/n 1501 a H-295B which after removal of the fuel injection was used to build c/n 1458.

Helio Dropped dropped their H-295B (1500 series) beause of low RPM problems but it appears that Republic Seabee figured out the problem.

Interestingly c/n 1458 was purchased by AL Wright  in 1978 and they went on to install several fuel injection systems using 337s and Field approvals. I think the first was c/n 1454. It appears, that it wasn't until using 337s became so difficult, that they developed the STC.

Also interesting is that the fuel injection system used on Wrights first conversion on c/n 1454 was identical to the one used on a a Republic RC-3 Seabee and the 337 lists that.

I think because of prior work by the Helio factory that when you put a fuel injection on a Helio H-295 You are converting it to a H-295B and the STC and other paperwork should reflect that, but thats MY opinion.


Doug Johnson

I just thought of something Louis' Helio C-GZZL c/n 1263 is probably the best Helio in the fleet, even better now.

It was repaired using an H-800 crash/cage fuselage and wings automatically upgrossing it to 3800lbs and using the wings with the Stainless carry though and improved upper attach bolts makes it stronger and eliminates the carry through AD. I've always thought it was a shame this wasn't offered as an option to address the carry through AD.

My main thought was Helio Enterprises inc when building the H-7/800 gave some serious thought to building a model H-600 with a GO-480 engine than a 300hp IO-540.

SO C-GZZL with the newer crash/cage fuselage would have been converted to an H-600  and with the fuel injection would now be a one of a kind model H-600B.

c/n 1289 was also converted to a H-600.


Thanks for the good words for GZZL.  As you said , it is good as is for 3800 pounds.  And the fuselage and wings are the same as the 4000 pounds H-800 (3800 on landing).  But it is not approved for 4000 since the power ratio and landing gear is the one of a 295.

A lot of work had to be done also on the frame by Mr. Noe to remove some steel box that were there to receive a tricycle gear configuration.   Probably with the same composite legs that were used for the tailwheel configuration.  My understanding is that the front wheel landing gear was never designed so there had never been such a tricycle configuration.  Except for that modified 700 amateur build that was so fun to look at.  So these steel parts were removed from the 800 frame to get rid of the useless weight. Returning the frame to a 295 frame.


Kevin Dunn


If I remember right, Ken (the guy you reference as Mr. Noe!) said it was around 30 pounds of steel that he removed off the cage of your airplane. I agree with Doug on this one, probably the best example in the fleet!



If you know Ken, please say hello to him from me


Kevin Dunn


Yes, he's a good friend. We stay in touch on a regular basis. I'll pass along your greetings.

I was at his place when he was building your airplane so I got to see it going together. I remember the patchwork paint that it had at the time. Looks a lot better now!


Doug Johnson 1

I ran across an interesting article on the fuel injection STC it lists some of the benefits and reasons you might want to consider the STC click on the link below


Hello, how much is the stc cost its self? Do you know if it can be used with the turbocharger stc?
Thanks Andrew