Heater Bypass Valve With Cabin Side Control Lever For RV-7 RV-8 And RV-9

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Part# 08-01311


The all stainless steel heater bypass box was conceived while looking at aluminum hardware used for sealing the firewall on experimental aircraft. It didn't make much sense to try to seal a stainless steel firewall with aluminum hardware. It is well known in the metal working world that stainless steel melts at 2600 degrees and aluminum melts at 1200 degrees. What most pilots don't know is that windblown avgas burns about 1875 degrees. And so, work on the all stainless steel heater bypass box began.

The all stainless box withstood the torturous flames for 10 minutes without failure. A good first test. Then the aluminum box was tested. In only 16 seconds the aluminum was a liquid puddle at the bottom of the simulated firewall. Only 16 seconds, you might not even know you have an engine fire in that time. This was an eye opener.

Once the all stainless steel heater bypass box was in production, the fun part began. Testing initially was a challenge because a simulated engine fire was required. But how hot does windblown avgas really burn? Our tests showed that windblown avgas burns at 1875 degrees. Now the test bed was in place.

Three models of the all stainless steel heater bypass boxes are offered. The engine side control lever comes with a backing plate that attaches to the cabin side of the firewall and has a 2 inch scat tube outlet so a tube can be attached in the cabin that directs air where wanted. The cabin side control unit is commonly used on RV7, RV8 and RV9 aircraft where the air is distributed in the cabin through a plenum. The RV-10 requires a special set of two that have offset levers to clear the upper nose gear mount.
California Prop 65 Warning Symbol

WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov.


  • All stainless steel construction offers a fireproof closure in case of an engine fire.
  • Designed with weight in mind, our stainless unit weighs 3.95 ounces and replaces the TG-10 aluminum box that weighs 3.28 ounces.
  • New flapper design offers better seal to keep out hot air when closed.
  • Direct replacement of the TG-10 aluminum unit. Easy replacement.


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Great quality

Radiocraft I Verified Purchase


August 13, 2023

This well made and very light

Larry R Verified Purchase


February 19, 2023

Fits in previously drilled holes, just a little smaller, much better quality, and seals better !

Kirk S
September 4, 2020

Great heat box to fit my needs and prevents yet another firewall penetration. As a suggestion one with a side mounted entry tube would be handy for space reasons.

Daniel M
October 12, 2017

Nicely made but this item does NOT contain SS mounting hardware! Directions state the following items are required to mount to a SS firewall: AN3C-4A (x2) AN960C-10L (x2) AN363C-1032 all metal stop nut (x2) Worth ordering concurrently to save on shipping costs.

August 17, 2018


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: What are the dimensions of the firewall mounting plate?

We have added the dimensional template to the documents tab of this web page. Please review them there.

Q: What size scat tube connects to 08-01311?

2 inch.

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