Interesting story about spinning a B-25 --> here.
In the category of "been there done that"—in a Baron, not a B-25—I know the feeling. My instructor was demonstrating Vmc and stalled in the process, the same as happened in the referenced story. At the time I didn't realize he'd done it unintentionally, and—from lack of experience—I didn't realize ehwas trying to kill us.
For the last few years I’ve flying fam and training hops in a C-45 for the FAA. Vmc is well above stall speed, as it is in the B-25, and there’s no excuse for departing the aircraft with one engine pulled back.
But out of curiosity, I tried yanking an engine in a B-25, below Vmc, using a simulator I fly, IL2. (It has the best flight physics of any sim I’ve flown, BTW. If you're inclined to such pastimes, I highly recommend it.)
Same setup as the story: dirty stall, cleaned her up, then chopped the power on the right side. She did spin, and did go over on her back— which if you think about is exactly what you’d expect. One wing is moving faster, thanks to the yaw, so it has more lift and over ya go.
But unlike Hennessy’s account I didn’t have any trouble recovering in the sim—unless I had a notch of flaps. Then I couldn’t stop the rotation or break the stall. The spin went real flat, but power on the opposite engine did help, after a fashion. However, as in the story, it did go back into a spin the opposite direction. I’m guessing the flaps blanket the rudders and elevator creating the loss of control.
I started the dirty simulation in the B-25 at 9,000 feet, and eventually crashed in the ocean. Tried it again retracting the flaps after 3 rotations, and recovered at 5,000.
I’m guessing that in Hennessey’s case someone looked to see if the bird was clean, realized it wasn’t, and sucked up the remaining flaps.
As wonderful as IL2 is, and as many hours of fun as I’ve had with it, I won’t claim it’s a 100% faithful model of the dozens of WW2 aircraft. But I got to fly a ‘51 yesterday: