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The General Electric CF34 high-bypass turbofan (used primarily on the Bombardier CRJ and Embraer E-Jet regional jets), unlike the vast majority of jet engines (both civil and military), is not certified to burn so-called “wide-cut” fuels (gasoline-kerosene blends, nowadays used mainly in cold-weather operations), such as Jet B1 and (formerly) JP-3 - only “narrow-cut” fuels (straight kerosenes), such as Jet A-1,2 Jet A, JP-5, and (formerly) JP-1. In contrast, CF34s in military service (known to the military as the TF34, and used mainly on the A-10 ground-attack aircraft) do just fine with wide-cut fuels (an absolute necessity back when aircraft so engined entered military service, as the go-to military jet fuel back then was JP-4, aka Jet B with the military’s stamp of approval).

This is a bit surprising, as:

  • it renders CF34-equipped aircraft unable to operate in very cold places (wide-cut fuels, having much lower freezing points and viscosities than the straight kerosenes, remain useable down to much lower temperatures than their narrow-cut ilk), and
  • there doesn’t seem to be any obvious technical reason for such a restriction, seeing how, as mentioned above, military CF34s are perfectly happy to run on wide-cut fuel.

Is there some critical difference between the military and civilian versions of the CF34 that renders wide-cut fuels compatible with the former but not the latter (maybe a gasket somewhere in the civilian CF34 that’s dissolved by the gasoline in wide-cut fuels?), or did General Electric simply not bother to certify the civilian version for use with wide-cut fuels?


1: Formerly also often known as “JP-4”.

2: Also often known as “JP-8”.

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    $\begingroup$ What is your source for saying it's not certified for wide-cut fuels? $\endgroup$
    – fooot
    Commented Jun 30, 2019 at 5:48

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Actually, the CF34-3B1 engines are certified to use wide-cut fuels, JetB/JP4. This comes straight out of the AOM for the CRJ200. I would venture to guess that all variants from CF34-1A to 3B would have the same certifications.

The CF34-8C5 engines on the other hand are not, again straight from the AOM for the CRJ 705/900. CF34-8C1 to 10E also likely have similar certifications for fuel certifications.

The difference is likely more to do with cost to certification. Seeing as wide-cut fuels aren’t overly common, except in the most remote locations north of 60 degrees of latitude, GE probably said why bother spending the extra money. JetA1 is good to -47*C/-53*F so for most commercial aviation, it’s more than sufficient. Every aircraft I’ve flown to date had an on-ground operating limitation of -40*C anyway.

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Wide-cut fuel is more flammable, so in a crash Jet-A would be safer.

CRJs can run on both just fine but from the limitations section of the manual, wide-cut is limited to ferry flights (non-revenue), so no people besides the crew.

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