Axial Stability of Flight Models In Game

[secretone]

I was recently rereading Duels in the Sky by Captain Eric Brown in which he describes the handling of various planes he test flew in real life and in which he also repeatedly discusses axial stability. This has started me wondering if the flight models we have in game are indeed accurate in terms of axial stability. My perception of what we have in game is neutral stability for the most part - a little trimming and you could fly on instruments. From what I have read in test pilot reports, many fighters had negative stability around one or more of the axes (lateral, longitudinal or vertical) and could be a real challenge to control. In fact, many writers seem to assert that poor axial stability was common and even a necessary evil in maneuverable fighters of that era. On the other hand, designers would want to have positive axial stability in bombers and especially transport planes. Today, of course, we have computer controlled fly by wire systems but that was not the case during the 1940's.

[JtD]

Most of the flight models are not accurate in terms of stability, I'd think. However, I could be wrong, because there's very little information available on the stabilities of all the aircraft we have in game. Based on what I've read I'd expect less stability as a trend, but it is hard to quantify "low" stability, in particular as the term describes more than one particular characteristic.

Stability can be good and you can still get a very manoeuvrable aircraft, this is more about control characteristics than stability.

[zipper]

All the planes in the game had some level of positive stability, the question was how much. Negative stability hasn't had a practical application until the advent of computer controlled fly-by-wire.

I think there is too little (mainly) directional stability across the board in the game, particularly at speed ... just based on my flying experience.

[JtD]

zipper, some planes had negative stability, too. There are may different types of stability, and planes can be perfectly save and even still fairly easy to fly without fly-by-wire with some sorts of negative stability. Check out the "spiral mode" - meaning a plane in straight and level flight trimmed for such has a tendency to lower one wing an go into a spiral, which will usually cause a descent and may result in a crash. This was common with single engined fighters of the era, and also common in game. It's not a problem for the pilot, unless he's unconscious, because this takes several minutes to become dangerous and is easily corrected with normal flying.

But in combination with CO poisoning or malfunctioning oxygen equipment or disorientation after a black out under high g or flying in clouds with poor instrumentation or iced up windows or ..., this may be deadly.

Directional stability of the fighters back then was also pretty poor compared to modern standards. It's one thing that is most commonly found in pilot comments when folks used to a modern day Cessna try out a warbird for the first time.

[secretone]

This sim has been so successful over the years because it has struck a good compromise between historical accuracy and playability. I crave greater accuracy and challenge as I learn more and more about the technologies and historical situations, but I am realistic enough to know that the game has to appeal to a wide audience and attract new players in order to remain viable.

[zipper]

zipper, some planes had negative stability, too. There are may different types of stability, and planes can be perfectly save and even still fairly easy to fly without fly-by-wire with some sorts of negative stability. Check out the "spiral mode" - meaning a plane in straight and level flight trimmed for such has a tendency to lower one wing an go into a spiral, which will usually cause a descent and may result in a crash. This was common with single engined fighters of the era, and also common in game. It's not a problem for the pilot, unless he's unconscious, because this takes several minutes to become dangerous and is easily corrected with normal flying.

But in combination with CO poisoning or malfunctioning oxygen equipment or disorientation after a black out under high g or flying in clouds with poor instrumentation or iced up windows or ..., this may be deadly.

Directional stability of the fighters back then was also pretty poor compared to modern standards. It's one thing that is most commonly found in pilot comments when folks used to a modern day Cessna try out a warbird for the first time.



OK ...

The post was about axial stability specifically, however. I interpreted that as static stability. Spiral stability is its own characteristic helped along by low, still positive, roll stability and low yaw damping with good positive directional stability.

"Immediately after taking the controls, however, I found the Mustang to be just as stable (or unstable, depending on your point of view) as the scores of bent and battered 172s I've rented over the years." Lt. Col. Dave Thole, U.S. Air Force (Retired), first time Mustang pilot. I imagine how one interprets general aircraft response may be a rather personal thing.

[JtD]

Certainly personal, but still an interesting statement. I've read it before, but it had slipped my mind, thanks for the reminder.

Also rgr on the rest.