Our B-25J is powered by two Wright R-2600-29, supercharged, 14 cylinder radial engines producing 1,700 HP each at takeoff power settings.  With the cowling panels removed for maintenance, you can see the twin row of cylinders .  Primarily air cooled, they also receive secondary cooling from scavenged engine oil run through coolers on the outboard section of the wing, then returned to the engines.  Also, rich fuel mixtures cool the engines at high power settings.

Here's a better look at the big Hamilton hydromatic propellers.  The props are 12 feet, 7 inches in diameter. 

They feature automatic constant-speed operation and can feather or unfeather quickly in an emergency.  The props can be adjusted from a low pitch of 22 degrees to a high pitch of 57 degrees and feather at 90 degrees.


After the war, some surplus B-25s were converted for civilian use by removing all military equipment, skinning over the bomb bay, installing a more passenger-friendly entry hatch, adding windows along both sides of the fuselage, and other passenger amenities.  It was from this postwar stock that most restored B-25's in existence today have derived.

In the course of this 'civilianization' process, the notoriously noisy engines (the Mitchell was called the loudest plane of WW II by many veterans) were significantly muffled by replacing the standard short stacks with a pair of half-ring exhaust collectors.   This change, plus extensive soundproofing, reduced the noise to a level that was acceptable to civilians.

Unlike the great majority of its airshow compatriots, 'Briefing Time' has been retrofitted with the original, wartime arrangement of a complete set of short stacks that encircle the cowling, as seen in the picture and top inset above.  The yellow-bordered inset shows another Mitchell airshow performer with the post-war collectors sported by most others. (Its nose-art and colors have been disguised - we don't want to embarrass anyone.)

When you see, and more to the point, hear 'Briefing Time' fly, as she does at numerous events each year, you will be hearing the true Mitchell roar as experienced by the crews who flew her in every theater of the war.

Click on the picture above to watch a video of 'Briefing Time' doing a "staged engine run-up"This involved Russ Strine running the engines at various RPM's ,from idle on up through ever higher RPM settings to nearly full takeoff power, all the while standing on the brakes .  Why torture the old girl this way?  It was done in an effort to record the sounds for the flight simulator version of 'Briefing Time' by the museum's in-house FS design team, MAAM-SIM.  Unfortunately, the camera was too close to the plane and the resulting sound quality was poor, necessitating another run-up from a longer distance at a later date.  But the visual is impressive, as it was shot at dusk and the flashes from the exhaust stacks are very dramatic.  The flight sim version even duplicates these exhaust flashes.

To hear a better representation of the mighty Cyclones' roar, play these brief wave (wav) files from the final version of the sound suite for the sim.   Warn the family, secure loose articles, then turn up the volume all the way up for just a hint of the actual thunder of the radials.

The first is of the engines at idle.  That "popping" noise is the distinctive sound made by these short stacks at idle speeds and disappear as the throttle is advanced.

This one is the sound of the engines at cruise, recorded inside the forward turret compartment, just behind the flight deck.

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