RSB40-094 Rev. 1

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Steve
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RSB40-094 Rev. 1

Post by Steve »

I don't know haw many of you have accomplished the above SB, which insulates the fuel line in the engine compartment between the engine-driven pump and the fuel servo. I was planning to do it during my next Annual Inspection, in August. Today I observed the issue that likely precipitated the SB. Flew for about 1.8 hours today, OAT 95 on the ground. After shutdown, I left the master on for a while and noticed that the fuel pressure (VM-1000) was going up quite a bit. over a couple of minutes, it rose from zero at shutdown, to 94 PSI and rising. I cracked the Mixture, and the pressure returned to zero. I'm sure that it would have continued to rise had I not opened the Mixture.

About a year and a half ago, my fuel pressure sensor failed after a ground stop (in hot weather). The failure mode was reading 6-8 PSI when the fuel pressure was zero, and about 6 PSI higher than usual with the engine running. I luckily had a spare sensor and replaced it and readings went back to normal. I researched the Honeywell sensor used in the VM-1000. It is a 50 PSI max sensor. The proof pressure for it is 2X that, or 100 PSI. In retrospect, I believe that the failure was caused by a post shutdown, heat soak-induced overpressure.

These sensors have been discontinued by Honeywell, so finding them is problematic. They are also quite expensive ($650 each from JPI - I think that they have one left in stock). I found some other sensors which have similar specs and could be substituted, but that would require a 337. I assume that the Garmin sensors are easier to source, but are still likely expensive.

So, I would encourage everyone (especially those with VM-1000 systems) to do this SB relatively soon, and in the hot summer months until then, maybe leave your Mixture open a crack after shutdown until the engine cools down a bit...
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TAILspin38
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Re: RSB40-094 Rev. 1

Post by TAILspin38 »

Thanks for the info Steve! My 06 DA40 will be going into annual in a few weeks. Is this something my mechanic will be easy enough to do/ does it require something specific? Things seem very difficult to get right now. We are in South Mississippi so our heat index the past week has been 105/110.
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Re: RSB40-094 Rev. 1

Post by Steve »

Anthony:

It looks pretty straightforward from the SB and Work Instruction:

http://support.diamond-air.at/fileadmin ... lation.pdf

All of the materials are pretty readily available except: P/N: PRF-20-12* - Reflective sleeve, which the Work Instruction specifies: *This part must be ordered from Diamond Aircraft. I ordered mine a couple of weeks ago, should have it in a few more days.
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Re: RSB40-094 Rev. 1

Post by jwx96 »

Thanks for the report! I was supposed to have the RSB done during my annual in May, but though a miscommunication it didn't get done. I have the VM1000. I'm going to schedule it.
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Re: RSB40-094 Rev. 1

Post by Rich »

Snce the post came out I've been monitoring the pressure post-shutdown. Most times there isn't any issue. It'll be sitting there at it's normal pressure of ~25 psi and maybe slowly bleed down. But today I had a case where it did as described. After shutdown the pressure started climbing right after shutdown. When it hit 35 psi I bled it off with the mixture control.

I have no idea why the difference in behaviors, but it does happen.
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Steve
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Re: RSB40-094 Rev. 1

Post by Steve »

My airplane is undergoing it's 19th Annual Inspection. I am in the midst of doing the RSB40-094 insulation of the fuel line. One interesting thing I noticed is that the SB shows one layer of firesleeve installed from the factory. Mine had no firesleeve on that portion of the fuel line (top photo). I've had the airplane since new, so I know that it wasn't removed at any point. I suppose there could have been a design change after 2001...

So, I installed that small diameter firesleeve, then the reflective sleeve (specific Diamond P/N). I'm waiting for a piece of the larger diameter firesleeve to arrive from Aircraft Spruce to reconnect the fuel line and finish the installation. Some photos:
Fuel line disconnected from engine-driven pump
Fuel line disconnected from engine-driven pump
Small diameter firesleeve installed
Small diameter firesleeve installed
Reflective sleeve installed
Reflective sleeve installed
Firesleeve clamp installed
Firesleeve clamp installed
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Steve
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Re: RSB40-094 Rev. 1

Post by Steve »

Just to finish this up, I completed the Service bulletin today by installing the large firesleeve over the fuel line. everything is back in place and leak test was good.
Front of engine where fuel flow sensor is located
Front of engine where fuel flow sensor is located
Fuel line running between engine and exhaust risers
Fuel line running between engine and exhaust risers
Fuel line at engine-driven fuel pump
Fuel line at engine-driven fuel pump
Hopefully, this will solve the post-shutdown heat soak and fuel pressure rise...
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Rich
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Re: RSB40-094 Rev. 1

Post by Rich »

Mine does have the narrow firesleeve but it only covers the front 2/3 or so of the fuel line. Interesting.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Steve
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Re: RSB40-094 Rev. 1

Post by Steve »

The only thing my airplane had installed before I did the SB was a 6" piece of split firesleeve wrapped around the fuel flow sensor (held in place with zip ties). That area shouldn't have been as hot as the side of the engine, where the fuel line runs between the crankcase and the exhaust risers. This arrangement looks much more substantial, but I guess that only time and experience will tell for sure. Luckily (?) we are having a record-breaking heat wave in TX (I think that today was the 57th day this year with a high of over 100 degrees F).

So, once the Annual is done, I will have lots of opportunity to see if it is effective at lowering the post-shutdown pressure rise...
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Rich
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Re: RSB40-094 Rev. 1

Post by Rich »

Steve, it appears your installation does not conform to the SB instructions. Instruction #9:

9. Install the reflective sleeve (item 2). The reflective sleeve should start against the aft end of the
existing large firesleeve. Do not insert the reflective sleeve under the large firesleeve.


Apparently that reflective sleeve is intended to reflect radiant heat and should be exposed. Per the picture in the SB:
Screen Shot 2022-08-13 at 11.17.28.png
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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