Kawa rough landing?

You're supposed to reduce the bank angle before attempting to increase
pitch.Â* Pulling back in a spiral dive almost guarantees wing failure.

On 9/21/2019 2:43 PM, 2G wrote:
On Saturday, September 21, 2019 at 1:24:28 PM UTC-7, Richard DalCanto wrote:
On Saturday, September 21, 2019 at 12:32:23 PM UTC-6, 2G wrote:
On Thursday, September 19, 2019 at 8:27:43 PM UTC-7, Andy Blackburn wrote:
Tom,

I think you misread my post. No one ever practices spins at pattern height and I'd never recommend it. My point was that practicing spins and spin entry and recovery at altitude might save your life should a moment of distraction in the pattern lead to a departure. Never practicing spins at all leads you to trying to figure everything out for the first time at low altitude should the worst happen. Early recognition is half the battle.

Andy

On Thursday, September 19, 2019 at 12:59:47 AM UTC-5, 2G wrote:
Andy,

When you are down low (in the pattern) practice COORDINATED flight - that is what will save your ass, not a low-altitude spin recovery. This is just plain, simple common sense. Pilots, lots of them, who don't do this are getting killed, this is fact. Can you produce a SINGLE pilot who has done such a low altitude save?

Tom
Andy,

I didn't misread your post, but I am certain you misread mine:

"We are all saying the same things, the ONLY difference is the emphasis on priorities. We all say that glider pilots should fly coordinated and be taught spin recognition and recovery. I am only pointing out that this isn't totally working because pilots are still killing themselves with low altitude stall-spins. Personally, this happened to a friend of mine, and I witnessed a second friend very nearly kill himself doing exactly this."

To repeat, spin recognition and recovery training should be taught (and practiced). But I think you would agree that it is far better not to enter the spin in the first place, especially at low altitude. As they say, an ounce of prevention is worth a pound of cure. Here is an attempted spin recovery that didn't work:
https://app.ntsb.gov/pdfgenerator/Re...Final&IType=LA

Tom
I agree that it is better to not spin in the first place. But I would not post that is a spin recovery that didn't work. Based on the report, it doesn't look like the pilot tried to recover correctly (or at all before turning into a spiral dive). I was amazed when I did spin training in Arizona how quickly a glider recovers as soon as you push the stick forward. This guy was flying in a competition with other gliders and had Marijuana, and Valium in his system. Luckily he didn't kill anybody else with his f*ing drug use. You don't want to know what I really think about dirt bags that fly or drive while impaired.
The NTSB stated that a blood sample was unavailable, so whether or not he was impaired could not be determined. If the NTSB couldn't determine that, I know you can't!

The spin recovery was attempted (this was witnessed), but was unsuccessful. High performance gliders build up speed very quickly - if you try to pull out of the dive too aggressively, which you are motivated to do avoid over-speeding the glider, you can overload the wings and rip them off. This is an inherent risk of practicing spin recoveries that hasn't been mentioned in this thread.

Tom

--
Dan, 5J

The Arcus M prop is very much bigger than the 26E prop. I have always assumed that is why it has a higher prop out and stopped sink rate.

I practised prop out landings in my 26E with no drama. I have never practised them in my Arcus, but on one occasion the engine failed to start; as usual I had committed to start at 1,000 ft over a landable field, and I landed in it safely without drama. (When the engine starts as normal my maximum height loss from starting to put the prop up is 100 ft).

In the Arcus there is an automated system for lowering the prop when you turn the ignition off to stop the engine. Apart from the one time the engine didn't start I have never tested whether the sink rate with the prop out and stopped is as bad as quoted.

The doors may be aligned with the airflow, but that big hole they are supposed to cover is a turbulence bucket.

After all, would SH design a glider with doors that reduce
the climb rate by 300 fpm?

Apparently, they did. 443 FPM sink rate is listed in the manual with doors open and mast up. 110 fpm is listed with a 50:1 L/D. Do the math.

On Thursday, September 19, 2019 at 3:11:04 PM UTC-4, Andreas Maurer wrote:
On Wed, 18 Sep 2019 15:16:31 -0700, Eric Greenwell
wrote:


I've never had anyone flying the usual PIK, DG, ASH, and Ventus self-launchers
mention plummeting or reduced control authority to me, but I'm sure there must be
some like that. What gliders have this plummet/control authority problem, and how
bad is the plummet (same as half spoiler, full spoiler, etc), and reduction in
control?

Arcus M - you ought to be able to find a operating handbook online.
WIth extended power plant the L/D decreases to 13/1 and minimum sink
rate to 443 fpm.

So far I've seen two DG-400s crash that were trying to land with
extended power plant and didn't reach the runway.

Cheers
Andreas

Some things to consider:

(1) The 'best' sink rate and LD with motor extended are at what speed?
Blue-line is what's quoted for many types, but that's typically much less
than minimum pattern speed, in turn much less than required for safe
round-out from high sink rate.

(2) Drag isn't just prop! In addition to gear doors, there's a
rather large radiator, plus the mast structure and lots of other
bits hanging out in the breeze.

(3) Some models have been fitted with different props over time.
So, your mileage (and plumetting) may vary.

The Ventus 2CM I owned was a real plummeter.
It had significantly reduced pitch and rudder authority
and reduced yaw stability with engine out.
In factory briefing I was warned to be extremely careful not to stall it .
ArcusM engine-out was much less exciting, by far.

I landed both motor out after assorted failures.
The ArcusM was no problem, but the V2CM was pretty exciting.

Hope that helps,
Best Regards, Dave

On 9/21/2019 2:30 PM, 2G wrote:
On Saturday, September 21, 2019 at 6:06:18 AM UTC-7,
wrote:
The main reason motorgliders like the Arcus see such a large decrease in
performance with the mast up is that the engine bay doors remain open,
and they are about six feet long. That's a huge amount of drag. When we
installed jet engines in the Tst-14 and four Arcuses, we had the main
doors close over the engine bay and two small "sub-doors" open around the
engine mount. With the engine extended, we measured the L/D of the Arcus
J (jet) at 38:1. The Arcus M gets 13:1 with engine extended.

The principal source of drag is the prop; the engine bay doors are aligned
with the slipstream, and doesn't matter how long they are, the frontal area
remains the same (very small)...
Because I've long been fascinated with aerodynamic drag, this particular topic
fascinates me, and the above exchange reminds me of a factoid my brain thinks
it has retained which - if retained accurately (too lazy to look it up just
now) - may surprise many a RASident. But first...

If the expression "there's devils in the details" applies anywhere,
aerodynamics fits the bill. And for the Truly Anal (or simply Seriously
Interested), I recommend the late Sighard F. Hoerner's masterpiece book,
"Fluid Dynamic Drag" which can be used to actually do a great job of assigning
numerical relative estimates of the drag contributions being discussed above.

I don't expect to actually make such an attempt, but I'm also not gonna bet
the retirement slush fund on "prop drag uber alles" in this instance, while I
*would* be willing to bet some actual money *against* the broad-brush
statement following the semi-colon of the shorter excerpt above being correct,
especially the "...doesn't matter how long they are..." bit.

Shape matters...a *lot* when it comes to aerodynamic drag. In drag-reduction
terms, whether it's more useful to (say) streamline the front of a
motorcycle/rider combo, or fair the rear may surprise many people. Consider a
theoretical, round, 1"-dia lift strut (think 2-33) vs. a faired version of the
same strut, both operating normal to the airflow, at pattern speeds. How many
RASidents would guess the drag coefficient of the former shape vs. the faired
shape is ... wait for it ...

.... == 8X == HIGHER?!? And - like hands in lowball poker, where you only
get worse - it (drag) all adds up!

If I ever get an Arcus M and the POH tells me it has an attention-getting sink
rate with the mast extended and inop engine at pattern speeds, I'm definitely
gonna incorporate some personal testing of that configuration early-on, with
gobs of altitude, in my getting-to-know-the-ship phase...and, in the purely
nut-behind-the-stick sense of things, I don't care *where* the drag sources
may actually be located!!! :-)

YMMV.
Bob W.

---
This email has been checked for viruses by AVG.
https://www.avg.com

"But, back to your claim that you can't enter a spin if you fly fast enough.."

Thats your claim of what I said, that's nowhere near to what I said.

I NEVER said a ship can't be stalled when flown fast, any dingbat should know that a common stall or an asymetrical stall can be induced at ANY airspeed. When the critical angle of attack is exceeded, she stops flying. What I said is that Energy Management is a more critical factor than coordination.

Go ahead and try to stall a bird which is being flown at 1.8 to 2 times its turning stall speed at a given angle of bank, iregardless of the position of your yaw string, and you will see your gonna have to put in some serious and noticable stick force. To get an accelerated stall ( and thats what it is) in that configuration, you know your doing something with the stick.

But the guy who is stumbling along slowly, inadvertently loosing airspeed, but flying ohhhh so very "coordinated", he is an accident just waiting to happen!! All he needs is just slight back pressure on that stick and woohooo off he is gonna fall!

You better take a little more care in how you "interpret" folks comments. It would save embarisment.

wrote on 9/21/2019 5:44 PM:
After all, would SH design a glider with doors that reduce
the climb rate by 300 fpm?

Apparently, they did. 443 FPM sink rate is listed in the manual with doors open and mast up. 110 fpm is listed with a 50:1 L/D. Do the math.

In addition to the doors, the mast and propeller contribute to the drag, as does
the landing gear and flap position. We have insufficient information for sorting
out the respective contributions to the sink rate,

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

Dave Nadler wrote on 9/21/2019 5:54 PM:
I landed both motor out after assorted failures.
The ArcusM was no problem, but the V2CM was pretty exciting.

What the reasons for such big differences?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

On Saturday, September 21, 2019 at 6:27:31 PM UTC-7, BobW wrote:
On 9/21/2019 2:30 PM, 2G wrote:
On Saturday, September 21, 2019 at 6:06:18 AM UTC-7,
wrote:
The main reason motorgliders like the Arcus see such a large decrease in
performance with the mast up is that the engine bay doors remain open,
and they are about six feet long. That's a huge amount of drag. When we
installed jet engines in the Tst-14 and four Arcuses, we had the main
doors close over the engine bay and two small "sub-doors" open around the
engine mount. With the engine extended, we measured the L/D of the Arcus
J (jet) at 38:1. The Arcus M gets 13:1 with engine extended.

The principal source of drag is the prop; the engine bay doors are aligned
with the slipstream, and doesn't matter how long they are, the frontal area
remains the same (very small)...
Because I've long been fascinated with aerodynamic drag, this particular topic
fascinates me, and the above exchange reminds me of a factoid my brain thinks
it has retained which - if retained accurately (too lazy to look it up just
now) - may surprise many a RASident. But first...

If the expression "there's devils in the details" applies anywhere,
aerodynamics fits the bill. And for the Truly Anal (or simply Seriously
Interested), I recommend the late Sighard F. Hoerner's masterpiece book,
"Fluid Dynamic Drag" which can be used to actually do a great job of assigning
numerical relative estimates of the drag contributions being discussed above.

I don't expect to actually make such an attempt, but I'm also not gonna bet
the retirement slush fund on "prop drag uber alles" in this instance, while I
*would* be willing to bet some actual money *against* the broad-brush
statement following the semi-colon of the shorter excerpt above being correct,
especially the "...doesn't matter how long they are..." bit.

Shape matters...a *lot* when it comes to aerodynamic drag. In drag-reduction
terms, whether it's more useful to (say) streamline the front of a
motorcycle/rider combo, or fair the rear may surprise many people. Consider a
theoretical, round, 1"-dia lift strut (think 2-33) vs. a faired version of the
same strut, both operating normal to the airflow, at pattern speeds. How many
RASidents would guess the drag coefficient of the former shape vs. the faired
shape is ... wait for it ...

... == 8X == HIGHER?!? And - like hands in lowball poker, where you only
get worse - it (drag) all adds up!

If I ever get an Arcus M and the POH tells me it has an attention-getting sink
rate with the mast extended and inop engine at pattern speeds, I'm definitely
gonna incorporate some personal testing of that configuration early-on, with
gobs of altitude, in my getting-to-know-the-ship phase...and, in the purely
nut-behind-the-stick sense of things, I don't care *where* the drag sources
may actually be located!!! :-)

YMMV.
Bob W.

---
This email has been checked for viruses by AVG.
https://www.avg.com

" I don't expect to actually make such an attempt, but I'm also not gonna bet
the retirement slush fund on "prop drag uber alles" in this instance, while I
*would* be willing to bet some actual money *against* the broad-brush
statement following the semi-colon of the shorter excerpt above being correct,
especially the "...doesn't matter how long they are..." bit."

Ok ,I ran that through Google translate, apparently it is Chinese for blah, blah, blah.