Playing around with the pitch phugoid

On Sunday, July 5, 2015 at 10:50:39 PM UTC-7, wrote:
You've blundered into the white room. You have primitive gyro guidance in the form of a turn rate indicator and so you are keeping the wings level, sort of. You are trimmed for 55 and the airspeed has just risen (alarmingly rapidly) to 85 and then temporaily plateaued there, staying constant for a couple of seconds. Answer quick: what do you do with the stick?

S

Flaps 90, pitch to hold 55 kts. Expect a 45-degree deck angle on emergence.

On Sunday, July 5, 2015 at 10:50:39 PM UTC-7, wrote:
You've blundered into the white room. You have primitive gyro guidance in the form of a turn rate indicator and so you are keeping the wings level, sort of. You are trimmed for 55 and the airspeed has just risen (alarmingly rapidly) to 85 and then temporaily plateaued there, staying constant for a couple of seconds. Answer quick: what do you do with the stick?

Wait, WTF are you trying to ask?

If you are planning to "blunder" into a cloud, you better know how to maintain attitude and airspeed via needle-ball and airspeed, if that is all you have in the cockpit.

Oh, and unless you are on an instrument flight plan (and trained and equipped) you are busting the FARs big time, so might as well declare an emergency and get ATC to give you a lot of room to screw up.

Then, fly the damn glider! Nothing primitive about needle & ball & airspeed, gliders do it all the time in other countries. If you can't control the airspeed, you should never have put yourself in the situation of being in a cloud!

It sounds like you are really worried about getting stuck IMC during a wave flight. If so, get a good T&B or even an attitude indicator, and some instruction under the hood in a power plane until you can safely fly on instruments.

Remember, the guy who lost it over Reno had tons of time IMC in fighter jets - and trust me they are not forgiving on the gauges - and he lost it when he went IMC....

Then you suggest to "push aggresively and hold the airspeed"! Really? That is a recipe for a quick trip past VNE! No **** "the airspeed will soon decrease rapidly" - when you impact the ground!

All this talk about benign spirals and phugoids are really BS - you HAVE TO FLY THE EFFING GLIDER, UNLESS YOU HAVE TERMINAL VELOCITY LIMITING DIVE BRAKES. PERIOD, DOT.

Arrrgggghh!!!

Kirk

On Wednesday, July 8, 2015 at 3:42:46 PM UTC-4, kirk.stant wrote:
On Sunday, July 5, 2015 at 10:50:39 PM UTC-7, wrote:
You've blundered into the white room. You have primitive gyro guidance in the form of a turn rate indicator and so you are keeping the wings level, sort of. You are trimmed for 55 and the airspeed has just risen (alarmingly rapidly) to 85 and then temporaily plateaued there, staying constant for a couple of seconds. Answer quick: what do you do with the stick?

Wait, WTF are you trying to ask?

If you are planning to "blunder" into a cloud, you better know how to maintain attitude and airspeed via needle-ball and airspeed, if that is all you have in the cockpit.

Oh, and unless you are on an instrument flight plan (and trained and equipped) you are busting the FARs big time, so might as well declare an emergency and get ATC to give you a lot of room to screw up.

Then, fly the damn glider! Nothing primitive about needle & ball & airspeed, gliders do it all the time in other countries. If you can't control the airspeed, you should never have put yourself in the situation of being in a cloud!

It sounds like you are really worried about getting stuck IMC during a wave flight. If so, get a good T&B or even an attitude indicator, and some instruction under the hood in a power plane until you can safely fly on instruments.

Remember, the guy who lost it over Reno had tons of time IMC in fighter jets - and trust me they are not forgiving on the gauges - and he lost it when he went IMC....

Then you suggest to "push aggresively and hold the airspeed"! Really? That is a recipe for a quick trip past VNE! No **** "the airspeed will soon decrease rapidly" - when you impact the ground!

All this talk about benign spirals and phugoids are really BS - you HAVE TO FLY THE EFFING GLIDER, UNLESS YOU HAVE TERMINAL VELOCITY LIMITING DIVE BRAKES. PERIOD, DOT.

Arrrgggghh!!!

Kirk

Ummmm...... chill a bit. Quite a few, "What if I went IFR in a sailplane" questions being bandied about recently.
1-A good pilot attempts to AVOID the "what if".
2-It won't be the first, or last, "issue" that "happens".
3-If it happens and the pilot is not equipped and trained, it's likely yet another front page issue.

I will admit "scud running" in a SEL many years ago. I knew the terrain and good landmarks so the issue of hitting a "granite cloud" were limited, still didn't mean I wasn't worried (got stuck between cloud layers over northern NJ coming from the south heading to my home airport in lower NYS).
Just because I did it does NOT mean I want to repeat it or condone it.

While I hate to see stupidity, nature has a way of dealing with it.......
Some say "Darwin", others say "God"..... either way, the end result is the same..... someone is DEAD....... "There is no such thing as gravity, the Earth sucks!".

I can understand the VERY LIMITED discussion for the, "Major WTF, it just happened" conversation, I feel for the most part it's someone trying to justify a "stupid frame of mind", nature/God will deal with it down the road.

BTW, when my step father had access to a, "pilot assessment questionnaire", he gave it to me. The results were, "You would make a GREAT fighter pilot, if I didn't know you better, I would NOT let you fly my planes......!".

I still fly his stuff, no, I have yet to break anything..... hope to continue the trend......

This discussion just keeps coming back..over and over and over...
Buy an electronic artificial horizon, full 3 dimensional like those offered with LX Varios (S80, etc.)
THEN
get some training in how to use it.

Trying to hand fly out of the "white room" is just plain nuts.
Trying to fly IFR with a compass and airspeed is just plain nuts.

I believe in "social darwinism."

ENOUGH with this dangerous line of discussion.

On Wednesday, July 8, 2015 at 3:06:51 PM UTC-5, Charlie M. (UH & 002
Ummmm...... chill a bit. Quite a few, "What if I went IFR in a sailplane" questions being bandied about recently.
1-A good pilot attempts to AVOID the "what if".
2-It won't be the first, or last, "issue" that "happens".
3-If it happens and the pilot is not equipped and trained, it's likely yet another front page issue.
snip

Ok, deep breath, fresh cup of coffee...

My frustration is with the OP's refusal to accept what has been proven over and over again in blood and bent metal: there is NO way to safely exit a fully developed IMC situation without either gyro instruments (and the skills to use them) or resorting to terminal dive brakes (rare these days) or maybe the retro method of a spin (in planes that will hold a stable spin long enough - also rare these days).

The benign spiral approach is fine in theory (anybody have any personal stories of using it for real to exit a cloud?) but is highly glider-specific and requires a stable starting condition - OK perhaps if you are trapped above or see that you are about to get trapped - but you better have practiced it A LOT before trying it for real - and it will do you no good once you have lost visual references and the airspeed and bank angle start to run away.

Sure, it's great to "what if" various scenarios. And I've done the same, and done my share of marginal flying in various aircraft in marginal conditions - and what I take from it is getting stuck unprepared in a cloud is about as bad as getting stuck in heavy sink in an unlandable box canyon - some things must be avoided at all costs!

Finally, what really got me was the OP's comment about pushing aggressively on the stick to control the airspeed. Maybe it's semantics, but to me that implies a forceful forward motion of the stick - which in my glider at cruise speed would bring the dead cats out of the bottom of the cockpit and result in a RAPID increase in airspeed to potentially dangerous levels. I wonder how often the OP has done speed sweeps in his glider, seeing how long it takes to accelerate from cruise to redline, and how little forward stick it take to do it?

Kirk
66

Interesting replies, thanks for chiming in.

I certainly agree that the phugoid is HUGELY damped by adding drag.

I would suggest that even some pilots who consider themselves well trained in "partial panel" flying, may not be really be familiar with the best way to end a pronounced pitch phugoid. And also may not appreciate the fact that in some sailplanes at some loadings, in the absence of pilot inputs, the pitch phugoid can tend to slowly get larger and larger, to the point where there is a stall break at the point of minimum airspeed. Even in a glider that seems quite well-behaved in normal visual flying.

If you disagree with my suggested inputs, I'd invite you to explore the phugoid a bit yourself. Accelerate or decelerate to 20 mph/ knots above or below the trimmed speed, let go the stick, and watch what happens.

I'd suggest that during a well-developed phugoid, if the airspeed is increasing (or is momentarily frozen and about to increase), the pilot ought be applying aft pressure on the stick, and if the airspeed is decreasing (or is momentarily frozen at a peak value and about to decrease), the pilot ought be applying forward pressure on the stick. I'd suggest that the very best opportunity for decisively breaking the phugoid is the moment where the airspeed peaks and as about to start decreasing. The glider is in a nearly level attitude at the "bottom" of an oscillation cycle at this instant. I'd suggest that if the airspeed is well above the trimmed airspeed at this moment, it will indeed take quite an "aggressive" push on the stick to freeze the airspeed at this moment. Then the glider can be slowly eased back to trim speed.

If this seems wrong to you, I'd invite you to explore the phugoid a bit yourself the next time you fly-- you might find the suggestion makes more sense after some hands-on explorations.

Or you may find that your glider is so dynamically stable at your loading, that the pitch phugoid is a non-issue.

S

PS "aggressive" is a relative turn. Whatever it takes to freeze the airspeed. Not enough to raise the dead cats to the canopy, but it's still a much larger input than you might at first think would be appropriate in a blind flying situation. The point is that at the point of maximum airspeed in a well-developed pitch phugoid, the glider is flying much faster than trimmed speed, and really wants to slow down by pulling up, and your job is to prevent that and then to slowly ease it down to a slower airspeed. Play around with it a bit and the ideas I posted may make a bit more sense. You have to see if first-hand in your own glider to really appreciate it.

S

Why are you playing with the pitch phugoid in a cloud? If you are flying the airplane, it won't get into a pitch phugoid in the first place. And if you are in a cloud, why would you let go of the stick?

It's simple (given you have a gyro turn indicator). Stop the turns. Control speed with pitch (drag helps). If you do get into a spiral and manage to roll out, expect a strong pitch up if over trim speed when you roll wings level.

This whole thread is absurd at best, dangerous at worst (people get ideas...)

Kirk
66

I must sheepishly admit that some years ago I allowed myself to become accidentally enveloped while flying the wave at Minden in a G103. I did indeed use the benign spiral to exit the cloud safely, after I considered other options to be exhausted. This involved a descent of over 1500 feet. It worked perfectly, and I consider that it saved my life -- I stupidly had no parachute with me on that flight. Even still, I can't recommend the procedure without reservation because it doesn't seem to work in all gliders, or even in that glider every time. But I can tell you that it worked once, even in turbulent conditions.


Lynn Alley
"2KA"

This sounds very interesting for a pilot testing a new design or getting
to know his new glider. It certainly doesn't seem to me to have any
relationship with day to day soaring. Or is this simply a mind experiment?

On 7/9/2015 8:51 AM, wrote:
Interesting replies, thanks for chiming in.

I certainly agree that the phugoid is HUGELY damped by adding drag.

I would suggest that even some pilots who consider themselves well trained in "partial panel" flying, may not be really be familiar with the best way to end a pronounced pitch phugoid. And also may not appreciate the fact that in some sailplanes at some loadings, in the absence of pilot inputs, the pitch phugoid can tend to slowly get larger and larger, to the point where there is a stall break at the point of minimum airspeed. Even in a glider that seems quite well-behaved in normal visual flying.

If you disagree with my suggested inputs, I'd invite you to explore the phugoid a bit yourself. Accelerate or decelerate to 20 mph/ knots above or below the trimmed speed, let go the stick, and watch what happens.

I'd suggest that during a well-developed phugoid, if the airspeed is increasing (or is momentarily frozen and about to increase), the pilot ought be applying aft pressure on the stick, and if the airspeed is decreasing (or is momentarily frozen at a peak value and about to decrease), the pilot ought be applying forward pressure on the stick. I'd suggest that the very best opportunity for decisively breaking the phugoid is the moment where the airspeed peaks and as about to start decreasing. The glider is in a nearly level attitude at the "bottom" of an oscillation cycle at this instant. I'd suggest that if the airspeed is well above the trimmed airspeed at this moment, it will indeed take quite an "aggressive" push on the stick to freeze the airspeed at this moment. Then the glider can be slowly eased back to trim speed.

If this seems wrong to you, I'd invite you to explore the phugoid a bit yourself the next time you fly-- you might find the suggestion makes more sense after some hands-on explorations.

Or you may find that your glider is so dynamically stable at your loading, that the pitch phugoid is a non-issue.

S

--
Dan Marotta