What is the triangle on a wire behind the rudder?

It looks like the test instrumentation that normally dangles far behind the airplane (aerodynamically far enough away that it's outside the strongest part of the wake and getting "clean," free stream air data), except it's reeled in for takeoff and landing.

It's the same idea as those giant pitot-static-vane probes sticking way out in front on some test airplanes. Here's a picture that makes a good illustration (took me some searching).



Think of the indicated airspeed vs calibrated airspeed correction chart in your airplane's manual. How did they figure out that the airspeed indicator reads 1 knot fast at this part of the chart, it's dead on at such-and-such airspeed, but over here 1½ knots slow? That's one of the things that comes from this kind of test instrumentation. In one of the 737 MAX threads we talked about the air data computers having airspeed correction tables for high angle of attack. That would be a good example of another thing to map during test.

It looks like the test instrumentation that normally dangles far behind the airplane (aerodynamically far enough away that it's outside the strongest part of the wake and getting "clean," free stream air data), except it's reeled in for takeoff and landing.

It's the same idea as those giant pitot-static-vane probes sticking way out in front on some test airplanes. Here's a picture that makes a good illustration (took me some searching).



Think of the indicated airspeed vs calibrated airspeed correction chart in your airplane's manual. How did they figure out that the airspeed indicator reads 1 knot fast at this part of the chart, it's dead on at such-and-such airspeed, but over here 1½ knots slow? That's one of the things that comes from this kind of test instrumentation.

Ah- thanks!

NASA paper on the topic here.

Are there any details on the construction of the pneumatic trailing static cone?

For example, is the tube open at the back inside the cone? Or does it have multiple openings around the side and the end is capped? And I would think the potential for spinning is a challenge.

On the ones I’ve used, the static ports are a couple feet ahead of the cone flush with the hose/line.

The cone is just the drag device. And yes, there is a swivel between the sensor and cone to accommodate spinning.

Elliot did a DIY version here.


[youtube]https://youtu.be/kZsi4A5PcTw[/youtube]

There's an unfortunate moment (about 0:55) in that video where he describes that they approached the folding wingtip like they do the rest of their flight control systems

It's an inboard aileron. They droop when Flaps 5 or more, so at rest they match the flaps profile since that's their new neutral.