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slow flight regime.................


gizzard
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Okay, now, don't ask why an ex-loady would ask such a question, or for that matter, even understand the principles it's based on, but still, here goes.............

After slow down on any airdrop operation, would the aircraft be in the slow flight regime, when attitude controls airspeed, and power controls altitude????? I would imagine this would be the case. As the load(s) exit the airplane the CG shifts and weight decreases must really make this a very active time for the pilot.......At normal troop, CDS and equipment drop altitudes, I can see where there is some room to allow for this and stay in the air... it must work, since i am still here, but what about LAPES, when you have maybe ten feet of altitude at the load extraction point....

Any thoughts?????

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From a purely technical perspective, attitude always controls airspeed and power always controls altitude. It's a little more dynamic than that in practice and it's easier to teach more traditional concepts, but in truth, technically, it's always attitude = airspeed and power = attitude. A great book is Stick & Rudder - been in continuous print since the '40s. Another good book is Contact Flying - I recommend both to pilots of every persuasion.

Traditional slow flight is a little bit slower than normal airdrop speeds and closer to threshold speed and expressed as a percentage of stall speed. So we're usually well above stall speeds during an airdrop.

The challeng with a CG shift of a large/heavy load is the change in angle of attack when you are closer to stalling at slow speed. However, most CG shifts due to load extraction are quick and quickly recovered from, so the actual danger of exceeding critical AoA and stalling is small.

I never got to do LAPES, it was out and then back briefly and then out again my first year or two in slicks. I have dropped MCADS which is well over 20,000lbs, so know first hand the significant CG shift with large/heavy loads. I can only imagine dealing with a LAPES CG shift of the same amount, or more, 10' off the ground. However, as we did MCADS in relatively close formation (200-300' on about a 45-60 degree line off the wing), I watched other planes often - there is typically a quick, small altitude gain as the load exits due to the change in CG pushing the tail down & nose up and the release of a large amount of weight. It seemed that 30-50' of altitude increase as the load exited was relatively common - I would assume the same was true during LAPES.

Back to stall speeds - we don't really stall based on speed, we stall when the AoA exceeds critical AoA - regardless of speed. When we slow down and suck the flaps up for a CDS drop, we are closer to stall than if the flaps are down - this is because with a clean wing, we have to have a higher AoA than with flaps 50%, to maintain level flight. Now, add in high elevations, like the some of the LCADS and LVCDS drops done in the mountains of AFG, and you're very, very near to stall. Despite what our -1-1 charts say about stall speeds (same speed all the way up to 10,000, 16,000, or 25,000 depending on your model of Herk), your AoA increases (along with a corresponding TAS increase) as you increase altitude. After talking with test pilots on the Herk about this very subject, they say the test flights are typically done at 10,000 and not interpolated down, so you have more 'pad' at low altitudes, but agree that you do lose margin as you go up in altitude. But therein lies the challenge of using speed as your sole reference to stall. In a perfect world, we'd have an AoA gauge to back up our ASI - I know the J-model has a dynamic barber pole on the bottom of their airspeed tape and I'd love to know the algorithm behind it.

Off on a tangent there, but I guess to bring it back to your question, we're typically not near enough to stalling during an airdrop for the CG shifts to pose much danger.

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Believe it or not, I understand all this......I could not remember, if I ever really knew, just how close to stall speed we dropped at.....so I guess the drops were not near the classical slow flight parameters that I guess i pretty much had in mind for approachs and landing............. Reckon I should confine my thoughts to the back of the bus!!!!! LOL!!!!!!

Thanks

Giz

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Believe it or not, I understand all this......I could not remember, if I ever really knew, just how close to stall speed we dropped at.....so I guess the drops were not near the classical slow flight parameters that I guess i pretty much had in mind for approachs and landing............. Reckon I should confine my thoughts to the back of the bus!!!!! LOL!!!!!!

Thanks

Giz

Hey Giz, off topic, but we watched a new TV show last night, "Arrow." Interesting concept for the story line. But last nights show involved the "hero" looking into firefighters that died suspiciously during fires.

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That has happened, there are even , shall we say, urban legends about firefighter versions of fragging..... Two rules of thumb......never go into a burning building with someone who is always wearin' bandaids, and, if possible, always go in with a guy you owe money to..............

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That has happened, there are even , shall we say, urban legends about firefighter versions of fragging..... Two rules of thumb......never go into a burning building with someone who is always wearin' bandaids, and, if possible, always go in with a guy you owe money to..............

Hey giz...can I borrow 20 bucks????

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Too late now!!!!!!!!!!!!!!!!!! I gotta say this...........it was probably a good thing that a lot of us on this site did not end up in the same place at the same time...........I do believe the result would have made some of Bob Daly's stories pale by comparison..............And he DOES have some beauts.....

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  • 1 month later...

During LAPES the problem wasn't stalling or a slow flight envelope but wheel heights.

When you put put a triple heavy married pallet off the bird at 36K its a huge shift nose up followed by a huge shift nose down when your at the optimum wheel height of 5 feet AGL, let me tell you that yoke moves from stop to stop in the blink of an eye and you have 5 feet to work with and not 50 or 60.

This is a problem because procedurally you have to maintain that wheel height until the load calls load clear (and by then the CG shift is done and over with) and the pilot call for the post extraction checklist, you just cant allow the 40 or 50 foot climb when the load exits (load as in cargo, not load as in loadmaster hopefully).

I missed LAPES when they did away with it, it was fun and you really got to see what the pilot was made of!!

The units that did LAPES had formal training syllabus's but I was stationed at Rhine Main in the 37th TAS when I did it, and you know what the formal training for LAPES in the 37th comprised?

Boss tells me "your doing LAPES tomorrow, read chapter 29 of your 55-130 then he walks away!!!! Boy that was a steep learning curve.

Edited by Dan Wilson
Kant spel
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