Many people consider that two is better than one. In fact a light twin has much more performance is more spacious and thus is more comfortable for passengers than a single one.
Nonetheless, and as Richard N. Aarons says, while single-engine aircraft may not be safer, twins can be more dangerous. I do agree when they are not operated correctly - of course - and when an engine is out at or close Vr in a hot day with full load.
When we lose one engine on a
twin, performance is not halved, but actually reduced by
80 percent or more.This 80-percent performance-loss is not just a
number, as we can easily demonstrate. And It's easy to explain this.
Let's consider that a light twin
which has an all-engine climb rate (sea level, ISA, max gross weight) of 1,600 fpm and a
single-engine climb rate under the same conditions of
300 fpm, the loss of climb performance in this case
is:
100-[(300/1600) x 100)]= 81,3%
The climb performance remaining is 18,7.
To achieve a 100/200 fpm single engine RoC after Vr one must comply at least with 5º bank to the live engine side ("raise the dead"), the dead engine immediately feathered and the aircraft "clean".
Considering a hot day at MTOW flying a twin with a rough and tear fuselage (that increases even more the drag) for sure we will not have a positive rate. When possible, taking off with Cowl flaps closed can give an extra 30-50 Fpm and this sometimes can make the difference....
I do consider it's better to hit a fence trying to land (on this circumstances), have some minor repairs to aircraft and walk away without injuries, than attempting with the impossible take-off.
Some time ago a PA31 chieftain was climbing through 9000 Ft when one engine flaed out few time after having departed. It was not able to return to the airport, crashing very close to the Rwy. On this situation the bad management of the energy and procedures were the cause of the fatal crash. It will be discussed on the next post.
The next table* shows some performance losses for twins with one engine out:
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