Can't remember much about 'em....
It's been over 35 years since I've flown a Navajo....both the straight
Navajo with the 310 HP engines and the Chieftan with the 350 hp engines.
But, I do recall the thing will not fly very well on one engine, unless you're
relatively light, and you're close to sea level. (Turbo charging helps, but it's not a cure-all.)
And, as I recall, it has the flight characteristic of a divergent fugoid on its longitudinal axis. Trying to remember the drama between the test pilot and Piper, when they were certifying the aircraft.
Not to push Cessna, but most Cessna twins will fly on one engine, albeit poorly. I flew the 310, 340, 401, 414. Again, this is pushing 40 years ago.
However....exceptions..... There's a thread currently here on PPrune about 'the runway behind you'. I remember taking off from El Paso one hot summer day....loaded to near max gross takeoff weight. This was in a C-414. About the time I reached for the gear handle, one engine quit. Thank God I took off from the end of a long runway....the plane was not flying well at all. (I'm guessing the density altitude was well over 8000 feet.) So, I dropped the gear, landed straight ahead on the runway, and got to a stop with maybe 1000 feet of runway remaining.
Many of these twins do not fly on one engine. The rest do a poor job. And, most, if not all, will not accelerate from lift-off speed to Vyse with
the gear down (on one engine). So, the reality is: Your "V1" in these airplanes (in practice) is when you have Vyse, an established rate-of-climb, and your hand off the throttles going for the gear handle. Agreed....not FAA standard, but in practice, it's what you have to do.
Fly safe,
PantLoad