Question: I get why the upper wing of a biplane is a compression member (because the flying wire is attached to it at an angle) but what I fail to understand is why the lower wing is the tension member of a truss of a biplane as explained [here](https://aviation.stackexchange.com/questions/19361/why-do-older-airplanes-have-a-wing-on-both-the-top-and-the-bottom-of-the-aircraf). So my question is why is the lower wing of a biplane referred to as a tension member of a struss?

![enter image description here](https://i.stack.imgur.com/j6s1H.jpg)

Answer: 
Before even taking off, a pilot is required to get a weather briefing, including winds. 
 Wind speeds are usually predictable and well known. If a pilot was flying against strong headwinds, with no good landing alternate, he screwed up his flight planning before he even started the engine. A headwind doesn't even have to be strong enough for negative GS, just strong enough to cause concern.

Winds vary by altitude in both strength and direction. If a pilot does find himself in such a situation, changing altitude by a few thousand feet, higher or lower, can very likely change both the wind direction and speed to something that is manageable.
If you are flying into a headwind, that means that there is an area of High pressure to your right. Frequently, as you leave move further away from the low pressure area, the winds will diminish. This isn't always the case, but it is the PICs responsibility to check weather conditions along the route and the routes to any alternate destinations.