Pulsejet Auxiliary Engine

Pulsejets are amazing: only a ramjet or solid-fuel rocket has a simpler design and they have drawbacks: a solid-fuel rocket is a safety hazard all by itself, and ramjets can't be operated at low speeds.

As an emergency or emergency-avoidance device for light aircraft, the pulsejet is close to perfect: lightweight, simple construction (it's a tube with a flap on one end), and can use the same fuel as the engine you're replacing/supplementing.

For takeoffs, simply extend the faired intakes in preparation; if you experience an engine-out too close to the ground simply punch the "ignite" button and your aircraft becomes a really loud jet aircraft that can turn and land again, safely. For inflight engine problems it gives you a *much* extended range to find an acceptable place to set down. Used in conjuction with a BRS system (a full-plane parachute) you can enjoy the most comprehensive coverage.

It can also be used as a "JATO" device if you're taking off from a short runway, though you will get complaints (and possibly a ticket, depending on local noise laws) if it isn't an emergency.