Getting out of the clouds in a Ventus C

I promised to test one of the ideas for getting out of clouds alive (from the thread on Lucky Chuckar). This one involved gear down, full spoilers, full cross control, and manage speed with the elevator (by listening).

Results:
In the above configuration, the Ventus C has a strong and abrupt tendency to go into a steep dive with stick full back. closing the spoilers with controls still fully crossed results in a dramatic pull-up. I did not have the flaps extended for this experiment.

Conclusion:
maintaining a safe attitude and controlling speed in this configuration is impossible. It does result in a rather impressive rate of descent though....

I might try this again with spoilers fully closed one day, with fresh underwear...

Matt

Wow!!
Somebody please explain the aerodynamics for this.
The spoilers spoil the flow over the elevator when at extreme yaw?
Heinz




On Friday, May 8, 2015 at 7:50:32 PM UTC-7, Matt Herron Jr. wrote:
I promised to test one of the ideas for getting out of clouds alive (from the thread on Lucky Chuckar). This one involved gear down, full spoilers, full cross control, and manage speed with the elevator (by listening).

Results:
In the above configuration, the Ventus C has a strong and abrupt tendency to go into a steep dive with stick full back. closing the spoilers with controls still fully crossed results in a dramatic pull-up. I did not have the flaps extended for this experiment.

Conclusion:
maintaining a safe attitude and controlling speed in this configuration is impossible. It does result in a rather impressive rate of descent though....

I might try this again with spoilers fully closed one day, with fresh underwear...

Matt

Yes.

Bert TW
Ventus cM

Test #2

Yesterday I tested a variant of the first test; Gear down, flaps to +2 (not landing flaps), spoilers NOT deployed, stick all the way back and left, rudder full right. I held the controls in this position without adjustment/input.

Results:
Plane went into an aggressive slip to the left, nose low. We did a slow, steady turn to the right for 2.5 revolutions. During that time pitch was stable. The nose came up a bit, then went down. the nose went down, but then came back up. Nothing dramatic. I think I lost about 1000ft/revolution. I will post the trace today.

Conclusion:
I personally would try this maneuver in clouds before bailing out. It seemed stable, with a high rate of decent. I don't know if I had elevator authority, as the stick was all the way back. I need to test the slip in the other direction to make sure the behavior is also stable (I tend to always drop the left wing on stall). Your milage will of course vary...

Anyone else want to try this?

Matt

On Sunday, May 10, 2015 at 8:44:59 AM UTC-7, Matt Herron Jr. wrote:
Test #2

Yesterday I tested a variant of the first test; Gear down, flaps to +2 (not landing flaps), spoilers NOT deployed, stick all the way back and left, rudder full right. I held the controls in this position without adjustment/input.

Results:
Plane went into an aggressive slip to the left, nose low. We did a slow, steady turn to the right for 2.5 revolutions. During that time pitch was stable. The nose came up a bit, then went down. the nose went down, but then came back up. Nothing dramatic. I think I lost about 1000ft/revolution.. I will post the trace today.

Conclusion:
I personally would try this maneuver in clouds before bailing out. It seemed stable, with a high rate of decent. I don't know if I had elevator authority, as the stick was all the way back. I need to test the slip in the other direction to make sure the behavior is also stable (I tend to always drop the left wing on stall). Your milage will of course vary...

Anyone else want to try this?

Matt

I'd like to try full cross control vs full dive brakes with everything else the same.

Andy

Andy, well, since I originally posted my Ventus B story I tried again the other day. It worked but airspeed indicator was blanked out completely by cross control. I didn't remember that happening before. However it was doable with sound alone. I didn't try it without the trailing edge dive brakes open and would guess that without the extra drag it would be harder to maintain slower airspeeds to reduce side loads on the tail and rudder. Any aerodynamicists out there that can do the rough calcs to see if load limits would be exceeded? Or are there even side load calcs available?

CH

You can'then exceed load limits by simple deflection far below manoeuvring speed. That's the definition of it.

With 900h on my Ventus, I would never fancy anything else than horizontal stabilisation with landing flaps followed by full airbrakes to get out of an IMC trap. Ever.

You can'then exceed load limits by simple deflection far below manoeuvring speed. That's the definition of it.

With 900h on my Ventus, I would never fancy anything else than horizontal stabilisation with landing flaps followed by full airbrakes to get out of an IMC trap. Ever.

You can'then exceed load limits by simple deflection far below manoeuvring speed. That's the definition of it.

With 900h on my Ventus, I would never fancy anything else than horizontal stabilisation with landing flaps followed by full airbrakes to get out of an IMC trap. Ever.

I find this thread very interesting.

Matt--

So the yaw string was streaming to the right, and the ship was slowly turning right?

What would you estimate the bank angle to be, and in which direction?

(To the left I presume, but "aggressive slip to the left" really only specifies the amount and direction of yaw string deflection, especially in a complex situation like this where direction of bank and direction of turn may be opposite.)

I experienced something very similar to this while playing around with full crossed controls in a Challenger ultralight. In the Challenger, the rudder went to full deflection, and stayed there, even WITHOUT any pilot input-- the adverse yaw from the ailerons set up a strong enough slip angle to blow the rudder all the way over to full deflection. We ended up turning slowly right, while banked slightly left, with the yaw string streaming way to the right, and full left ailerons held to cancel the right roll torque from sideslip + dihedral, and the rudder blown all the way over to the right.

I'd like for some more people to try this and report back.

Keep in mind the importance of leaving the spoilers closed-- see the O.P. on this thread.

But for an added test of robustness-- what happens if you initiate the maneuver in the OPPOSITE bank that you expect to end up in-- say begin in a right bank/turn and THEN apply full left aileron and full right rudder? In other words how far can the aircraft be perturbed from the steady-state, in terms of bank angle, and still return to the steady state?

By the way, here are some related threads, just to put them all in once place:

Chukar's own account -- includes CH's original suggestion re fully crossed controls to enter a stable spiral in clouds--
http://groups.google.com/forum/#!top...ng/LFr-fXMjoMc --


In wave, in blue hole at cloud level, hole closes, in IMC, then what? -- includes much discussion of the benign spiral maneuver--
https://groups.google.com/forum/#!to...ng/ALP7WFf3GYs


Emergency instrumentation for cloud encounters-- O.P. referenced a simple piezoelectric turn rate indicator, branched off into an extensive discussion of the artificial horizon capability built into some of the top-of-the-line varios--
https://groups.google.com/forum/#!to...ng/b0RXcbDa8ik

Needed: Inexpensive AHRS module to work with Oudie, XCsoar, LK8000, etc...--discussion of how to create an artificial horizon capability if you aren't flying with a vario with such capability built-in
https://groups.google.com/forum/#!to...ng/B-W-MMSf7V4


On Sunday, May 10, 2015 at 10:44:59 AM UTC-5, Matt Herron Jr. wrote:
Test #2

Yesterday I tested a variant of the first test; Gear down, flaps to +2 (not landing flaps), spoilers NOT deployed, stick all the way back and left, rudder full right. I held the controls in this position without adjustment/input.

Results:
Plane went into an aggressive slip to the left, nose low. We did a slow, steady turn to the right for 2.5 revolutions. During that time pitch was stable. The nose came up a bit, then went down. the nose went down, but then came back up. Nothing dramatic. I think I lost about 1000ft/revolution.. I will post the trace today.

Conclusion:
I personally would try this maneuver in clouds before bailing out. It seemed stable, with a high rate of decent. I don't know if I had elevator authority, as the stick was all the way back. I need to test the slip in the other direction to make sure the behavior is also stable (I tend to always drop the left wing on stall). Your milage will of course vary...

Anyone else want to try this?

Matt