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Comment by redis_mlc | Hacker News Reader

> one of best balanced planes out there

Airliner design is regulated for stability for passenger flight on IFR approaches. So they're all pretty smooth.

(The reason for the 737 MAX MCAS system was to meet those requirements, although they failed in that case.)

All planes can glide if the wings are attached, and any essential electricity is available for control (if necessary.)

A corollary of "all planes glide" is that planes cannot really fall or dive straight (vertically) down from an appreciable height with the wings attached. A good story to tell passengers afraid of flying.

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All planes can glide, but not to the same degree. The glide ratio, or the ratio between distance travelled per distance dropped, varies wildly between planes.

A purpose built glider has a glide ratio of about 60:1, so it could travel 60mi while only losing 1mi of altitude, while a Cessna 172 has a glide ratio of 9. Large passenger aircraft have glide ratios inbetween, with a 737 having a ratio of 17.

On the other extreme end you have military fighter planes, which tend to more closely resemble well propelled un-aerodynamic objects once their engines give out. The worst I could find was the F104 Starfighter, which has a glide ratio of 3-5 depending on its exact configuration. Dead stick landings of these aircraft tend to be rare, as the availability of ejection seats (especially before zero-zero seats became a thing) encourages a not-my-problem-any-more attitude among pilots who discover themselves absent a working engine.

> On the other extreme end you have military fighter planes, which tend to more closely resemble well propelled un-aerodynamic objects once their engines give out.

Which made this all the more impressive:

https://theaviationist.com/2014/09/15/f-15-lands-with-one-wi...

Really highlights how important high thrust:weight ratios are for military aircraft. Missing a wing? Apply afterburner

It is worth pointing out that many military aircraft are made to be unstable by design. Unpowered or underpowered Commercial aircraft want to glide, with aerodynamic resisting change of course for safety and ease of use. On the other hand, aerodynamics of military combat aircraft operate in unstable equilibrium to encourage greater maneuverability.

For sure. Modern military aircraft are so unstable that they’re unflyable without computers. And that’s not just because computers directly control the control surfaces, but because humans would really struggle to stabilize the aircraft on reaction speed alone.

> which tend to more closely resemble well propelled un-aerodynamic objects once their engines give out.

With sufficient thrust pigs fly just fine

With well vectored thrust, you don’t even need wings. Heck, that’s literally how rockets work.

Wings and tail, of course: https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261

And assuming the wings haven’t lost their lift due to ice: https://en.wikipedia.org/wiki/American_Eagle_Flight_4184

Planes can glide, but there’s still lots of ways to drive one straight into the ground.

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