On 10/6/2023 7:55 AM, Dave Nadler wrote:
> An excellently written accident report worth reading:
> https://bea.aero/fileadmin/user_upload/D-KWAY_en.pdf
>

Having recently lost a longish-time, gliderport-compadre to what appears to
have been uncontrolled "flight" into (survivably-landable) terrain in a
similar ship - mast appearing to've been at least partially extended - both
these crunches (and many, many, more over the years) tend to confirm my
long-held working conclusion that Joe Pilot has to work really, really, hard
to come up with new-n-creative ways to have accidents.

That's not by way of assigning blame, but by way of trying to "NOT go there"
myself. My recently-demised gliderport-compadre was 71 and (lifelong?) of
"slightly chubby" aspect (i.e. far from morbidly obese). Predictably, one of
the first speculations I encountered in the wake of his crash was "can't rule
out a medical event"...and indeed I cannot/do-not. But any glider pilot taking
personal comfort in that possibilty is - IMO - discounting an elephant in the
room: it might *NOT* have been medical. "Kids, don't DO that!"

Be careful out there, indeed...

What are the chances that we will get such a detailed accident report anytime soon for the Colorado accident Bob is referring to? There is a preliminary NTSB report with some details, but the most important question remains if the engine contributed to the accident.

Ramy

On Friday, October 6, 2023 at 9:13:13 AM UTC-7, BobW wrote:
> On 10/6/2023 7:55 AM, Dave Nadler wrote:
> > An excellently written accident report worth reading:
> > https://bea.aero/fileadmin/user_upload/D-KWAY_en.pdf
> >
> Having recently lost a longish-time, gliderport-compadre to what appears to
> have been uncontrolled "flight" into (survivably-landable) terrain in a
> similar ship - mast appearing to've been at least partially extended - both
> these crunches (and many, many, more over the years) tend to confirm my
> long-held working conclusion that Joe Pilot has to work really, really, hard
> to come up with new-n-creative ways to have accidents.
>
> That's not by way of assigning blame, but by way of trying to "NOT go there"
> myself. My recently-demised gliderport-compadre was 71 and (lifelong?) of
> "slightly chubby" aspect (i.e. far from morbidly obese). Predictably, one of
> the first speculations I encountered in the wake of his crash was "can't rule
> out a medical event"...and indeed I cannot/do-not. But any glider pilot taking
> personal comfort in that possibilty is - IMO - discounting an elephant in the
> room: it might *NOT* have been medical. "Kids, don't DO that!"
>
> Be careful out there, indeed...

On Saturday, October 7, 2023 at 12:40:33 PM UTC-4, Dave Nadler wrote:
> On Friday, October 6, 2023 at 4:13:22 PM UTC-4, Ramy wrote:
> > What are the chances that we will get such a detailed accident report anytime soon
> > for the Colorado accident Bob is referring to? There is a preliminary NTSB report
> > with some details, but the most important question remains
> > if the engine contributed to the accident.
> I've seen no *evidence* that the engine contributed to that accident.
> The engine *may* have been in the (relatively low drag) cooling position.
>
> An important note, though probably not relevant to the specific accident
> Bob mentioned; Current certification requirements do NOT require,
> for engine deployed and not running:
> - stall and spin testing (with verification of acceptable handling),
> - any minimum sink rate,
> - trim authority for pattern speed
> These points were discussed and acknowledged at the OSTIV SDP
> meeting last week.
>
> Hope that helps,
> Best Regards, Dave
I have some pretty good information on this tragic event, what you are likely to read is that the engine was deployed and the pilot spun in from a low altitude. Unlikely that there was anything medically contributed to the accident. Old Bob, The Purist

On Saturday, October 7, 2023 at 1:35:34 PM UTC-7, youngbl...@gmail.com wrote:
> On Saturday, October 7, 2023 at 12:40:33 PM UTC-4, Dave Nadler wrote:
> > On Friday, October 6, 2023 at 4:13:22 PM UTC-4, Ramy wrote:
> > > What are the chances that we will get such a detailed accident report anytime soon
> > > for the Colorado accident Bob is referring to? There is a preliminary NTSB report
> > > with some details, but the most important question remains
> > > if the engine contributed to the accident.
> > I've seen no *evidence* that the engine contributed to that accident.
> > The engine *may* have been in the (relatively low drag) cooling position.
> >
> > An important note, though probably not relevant to the specific accident
> > Bob mentioned; Current certification requirements do NOT require,
> > for engine deployed and not running:
> > - stall and spin testing (with verification of acceptable handling),
> > - any minimum sink rate,
> > - trim authority for pattern speed
> > These points were discussed and acknowledged at the OSTIV SDP
> > meeting last week.
> >
> > Hope that helps,
> > Best Regards, Dave
> I have some pretty good information on this tragic event, what you are likely to read is that the engine was deployed and the pilot spun in from a low altitude. Unlikely that there was anything medically contributed to the accident. Old Bob, The Purist

This sounds like, “Safety margin creep”, to me. The guy couldn’t be more current with tons of hours in type, having owned the ship for years. I happened to me! My absolute minimum altitude to stop turning was a hard 300’, after watching a Ventus thermal right into the ground at Cal City!
After hitting a good bump at 300’ while turning final, I stayed with my minimum altitude to stop turning and landed at Sweetwater strip in the Sierras. Fifteen minutes later, I watched another ship, hit the same bump, turn in it, and CLIMB AWAY!
My absolute minimum altitude suddenly moved over to the Usually /maybe column!
We can rationalize/ out-think ourselves right into the ground!
JJ

On Saturday, October 7, 2023 at 1:35:34 PM UTC-7, youngbl...@gmail.com wrote:
> On Saturday, October 7, 2023 at 12:40:33 PM UTC-4, Dave Nadler wrote:
> > On Friday, October 6, 2023 at 4:13:22 PM UTC-4, Ramy wrote:
> > > What are the chances that we will get such a detailed accident report anytime soon
> > > for the Colorado accident Bob is referring to? There is a preliminary NTSB report
> > > with some details, but the most important question remains
> > > if the engine contributed to the accident.
> > I've seen no *evidence* that the engine contributed to that accident.
> > The engine *may* have been in the (relatively low drag) cooling position.
> >
> > An important note, though probably not relevant to the specific accident
> > Bob mentioned; Current certification requirements do NOT require,
> > for engine deployed and not running:
> > - stall and spin testing (with verification of acceptable handling),
> > - any minimum sink rate,
> > - trim authority for pattern speed
> > These points were discussed and acknowledged at the OSTIV SDP
> > meeting last week.
> >
> > Hope that helps,
> > Best Regards, Dave
> I have some pretty good information on this tragic event, what you are likely to read is that the engine was deployed and the pilot spun in from a low altitude. Unlikely that there was anything medically contributed to the accident. Old Bob, The Purist
What information causes you to rule out a medical issue?

As an eye witness to my former partner's low altitude stall/spin in our
LS-6a, I can honestly state that the condition of the wreckage of Dave's
ASH-26e looked identical. Note the broken aft left wing and destroyed
cockpit. My partner was, indeed, fortunate to have survived.

I will wait for the official cause of the crash but, discounting a
medical cause, I'll bet it was a low altitude stall/spin.

Dan
5J

On 10/9/23 08:49, John Sinclair wrote:
> On Saturday, October 7, 2023 at 1:35:34 PM UTC-7, youngbl...@gmail.com wrote:
>> On Saturday, October 7, 2023 at 12:40:33 PM UTC-4, Dave Nadler wrote:
>>> On Friday, October 6, 2023 at 4:13:22 PM UTC-4, Ramy wrote:
>>>> What are the chances that we will get such a detailed accident report anytime soon
>>>> for the Colorado accident Bob is referring to? There is a preliminary NTSB report
>>>> with some details, but the most important question remains
>>>> if the engine contributed to the accident.
>>> I've seen no *evidence* that the engine contributed to that accident.
>>> The engine *may* have been in the (relatively low drag) cooling position.
>>>
>>> An important note, though probably not relevant to the specific accident
>>> Bob mentioned; Current certification requirements do NOT require,
>>> for engine deployed and not running:
>>> - stall and spin testing (with verification of acceptable handling),
>>> - any minimum sink rate,
>>> - trim authority for pattern speed
>>> These points were discussed and acknowledged at the OSTIV SDP
>>> meeting last week.
>>>
>>> Hope that helps,
>>> Best Regards, Dave
>> I have some pretty good information on this tragic event, what you are likely to read is that the engine was deployed and the pilot spun in from a low altitude. Unlikely that there was anything medically contributed to the accident. Old Bob, The Purist
>
> This sounds like, “Safety margin creep”, to me. The guy couldn’t be more current with tons of hours in type, having owned the ship for years. I happened to me! My absolute minimum altitude to stop turning was a hard 300’, after watching a Ventus thermal right into the ground at Cal City!
> After hitting a good bump at 300’ while turning final, I stayed with my minimum altitude to stop turning and landed at Sweetwater strip in the Sierras. Fifteen minutes later, I watched another ship, hit the same bump, turn in it, and CLIMB AWAY!
> My absolute minimum altitude suddenly moved over to the Usually /maybe column!
> We can rationalize/ out-think ourselves right into the ground!
> JJ

On Saturday, October 7, 2023 at 9:40:33 AM UTC-7, Dave Nadler wrote:
> On Friday, October 6, 2023 at 4:13:22 PM UTC-4, Ramy wrote:
> > What are the chances that we will get such a detailed accident report anytime soon
> > for the Colorado accident Bob is referring to? There is a preliminary NTSB report
> > with some details, but the most important question remains
> > if the engine contributed to the accident.
> I've seen no *evidence* that the engine contributed to that accident.
> The engine *may* have been in the (relatively low drag) cooling position.
>
> An important note, though probably not relevant to the specific accident
> Bob mentioned; Current certification requirements do NOT require,
> for engine deployed and not running:
> - stall and spin testing (with verification of acceptable handling),
> - any minimum sink rate,
> - trim authority for pattern speed
> These points were discussed and acknowledged at the OSTIV SDP
> meeting last week.
>
> Hope that helps,
> Best Regards, Dave
While certification may not require it, at least in the case of the ASH26E: It was tested for stall and spin with engine running and not running (and gives recovery procedures in the manual), the sink rate with engine deployed and not running is quoted in the manual, and there is plenty of trim authority for pattern speed regardless of engine status.

In the accident on Colorado, the crash site is in the middle of a large, open and landable field. In the accident in Germany, the glider encountered trees trying to make it back to the runway. Quite different conditions, and at least the last minute of flight also appears to be quite different.

On Monday, October 9, 2023 at 10:30:51 AM UTC-7, jfitch wrote:
> On Saturday, October 7, 2023 at 9:40:33 AM UTC-7, Dave Nadler wrote:
> > On Friday, October 6, 2023 at 4:13:22 PM UTC-4, Ramy wrote:
> > > What are the chances that we will get such a detailed accident report anytime soon
> > > for the Colorado accident Bob is referring to? There is a preliminary NTSB report
> > > with some details, but the most important question remains
> > > if the engine contributed to the accident.
> > I've seen no *evidence* that the engine contributed to that accident.
> > The engine *may* have been in the (relatively low drag) cooling position.
> >
> > An important note, though probably not relevant to the specific accident
> > Bob mentioned; Current certification requirements do NOT require,
> > for engine deployed and not running:
> > - stall and spin testing (with verification of acceptable handling),
> > - any minimum sink rate,
> > - trim authority for pattern speed
> > These points were discussed and acknowledged at the OSTIV SDP
> > meeting last week.
> >
> > Hope that helps,
> > Best Regards, Dave
> While certification may not require it, at least in the case of the ASH26E: It was tested for stall and spin with engine running and not running (and gives recovery procedures in the manual), the sink rate with engine deployed and not running is quoted in the manual, and there is plenty of trim authority for pattern speed regardless of engine status.
>
> In the accident on Colorado, the crash site is in the middle of a large, open and landable field. In the accident in Germany, the glider encountered trees trying to make it back to the runway. Quite different conditions, and at least the last minute of flight also appears to be quite different.

Hey guys,
The pilot wasn’t killed! He survived and made a statement to the authorities that didn’t mention any medical issues or spinning in!
Read the complete report on Dave’s post!
JJ

JJ we discussing 2 separate ASH26 accidents in this thread. The one at Colorado a month or so ago was fatal.

Ramy

On Monday, October 9, 2023 at 12:34:16 PM UTC-7, John Sinclair wrote:
> On Monday, October 9, 2023 at 10:30:51 AM UTC-7, jfitch wrote:
> > On Saturday, October 7, 2023 at 9:40:33 AM UTC-7, Dave Nadler wrote:
> > > On Friday, October 6, 2023 at 4:13:22 PM UTC-4, Ramy wrote:
> > > > What are the chances that we will get such a detailed accident report anytime soon
> > > > for the Colorado accident Bob is referring to? There is a preliminary NTSB report
> > > > with some details, but the most important question remains
> > > > if the engine contributed to the accident.
> > > I've seen no *evidence* that the engine contributed to that accident.
> > > The engine *may* have been in the (relatively low drag) cooling position.
> > >
> > > An important note, though probably not relevant to the specific accident
> > > Bob mentioned; Current certification requirements do NOT require,
> > > for engine deployed and not running:
> > > - stall and spin testing (with verification of acceptable handling),
> > > - any minimum sink rate,
> > > - trim authority for pattern speed
> > > These points were discussed and acknowledged at the OSTIV SDP
> > > meeting last week.
> > >
> > > Hope that helps,
> > > Best Regards, Dave
> > While certification may not require it, at least in the case of the ASH26E: It was tested for stall and spin with engine running and not running (and gives recovery procedures in the manual), the sink rate with engine deployed and not running is quoted in the manual, and there is plenty of trim authority for pattern speed regardless of engine status.
> >
> > In the accident on Colorado, the crash site is in the middle of a large, open and landable field. In the accident in Germany, the glider encountered trees trying to make it back to the runway. Quite different conditions, and at least the last minute of flight also appears to be quite different.
> Hey guys,
> The pilot wasn’t killed! He survived and made a statement to the authorities that didn’t mention any medical issues or spinning in!
> Read the complete report on Dave’s post!
> JJ

This sounds classic and has been done many times before. I recall a DG800 going into the tree short of intended field with the engine out. Pilot tried to start the engine and failed. He called the field and asked for help getting a ride, replied...soon as we hook up your trailer we will be on the way. His reply, no need for the trailer, the glider is still in the trees!!

I fly a DG800 and never shut the engine down more than a 10:1 glide to a known landable field. 17 years now, knocking on wood, it has kept me out of trouble.

Buzz Graves

On Tuesday, October 10, 2023 at 1:18:51 PM UTC-7, BG wrote:
> This sounds classic and has been done many times before. I recall a DG800 going into the tree short of intended field with the engine out. Pilot tried to start the engine and failed. He called the field and asked for help getting a ride, replied...soon as we hook up your trailer we will be on the way. His reply, no need for the trailer, the glider is still in the trees!!
>
> I fly a DG800 and never shut the engine down more than a 10:1 glide to a known landable field. 17 years now, knocking on wood, it has kept me out of trouble.
>
> Buzz Graves
Looking at the GPS trace and average glide for each segment, before and after the engine was deployed, it answers another string in the past who said they had a 20:1 glide with the engine out in a similar glider. The glide trace says 11:1 with the engine out. Stacks up well with my own experiences and margin I use if the engine is not working and out.

Buzz Graves

On Tuesday, October 10, 2023 at 5:39:28 PM UTC-7, BG wrote:
> On Tuesday, October 10, 2023 at 1:18:51 PM UTC-7, BG wrote:
> > This sounds classic and has been done many times before. I recall a DG800 going into the tree short of intended field with the engine out. Pilot tried to start the engine and failed. He called the field and asked for help getting a ride, replied...soon as we hook up your trailer we will be on the way. His reply, no need for the trailer, the glider is still in the trees!!
> >
> > I fly a DG800 and never shut the engine down more than a 10:1 glide to a known landable field. 17 years now, knocking on wood, it has kept me out of trouble.
> >
> > Buzz Graves
> Looking at the GPS trace and average glide for each segment, before and after the engine was deployed, it answers another string in the past who said they had a 20:1 glide with the engine out in a similar glider. The glide trace says 11:1 with the engine out. Stacks up well with my own experiences and margin I use if the engine is not working and out.
>
> Buzz Graves
The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!

> The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!

Another major factor is whether the prop is windmilling or stopped. A windmilling prop adds almost the flat plate surface of its swept area. A large drag reduction is had by stopping to prop, and of course even more by stowing it. If one can't stop it due to a broken belt or whatever, they laying in down nets a large gain in L/D over a windmilling prop.

bumper

On Wednesday, October 11, 2023 at 7:08:13 AM UTC-7, bumper wrote:
> > The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!
> Another major factor is whether the prop is windmilling or stopped. A windmilling prop adds almost the flat plate surface of its swept area. A large drag reduction is had by stopping to prop, and of course even more by stowing it. If one can't stop it due to a broken belt or whatever, they laying in down nets a large gain in L/D over a windmilling prop.
>
> bumper

That's a really interesting observation, and simultanously intuitive, and not to my mind. If the prop is stopped, then you have a stalled plate the shape of a prop in the airflow - so I guess the impact of that is pretty obvious. But when the prop is windmilling, the leading edge of the prop is experiencing airflow, which should be a smaller cross section. Except that it's also doing "work". I'm sure that there's sufficient experiential data about the behavior and impact of windmilling props to confirm that it's worse than a stopped one, but does anyone have a clear aerodynamic explanation of why it should be so?

On Wednesday, October 11, 2023 at 12:19:01 PM UTC-4, Doug Bailey wrote:
> ...I'm sure that there's sufficient experiential data about the behavior and
> impact of windmilling props to confirm that it's worse than a stopped one....
https://www.peter2000.co.uk/aviation/misc/prop.pdf

On Wednesday, October 11, 2023 at 8:19:01 AM UTC-8, Doug Bailey wrote:
> On Wednesday, October 11, 2023 at 7:08:13 AM UTC-7, bumper wrote:
> > > The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!
> > Another major factor is whether the prop is windmilling or stopped. A windmilling prop adds almost the flat plate surface of its swept area. A large drag reduction is had by stopping to prop, and of course even more by stowing it. If one can't stop it due to a broken belt or whatever, they laying in down nets a large gain in L/D over a windmilling prop.
> >
> > bumper
> That's a really interesting observation, and simultanously intuitive, and not to my mind. If the prop is stopped, then you have a stalled plate the shape of a prop in the airflow - so I guess the impact of that is pretty obvious. But when the prop is windmilling, the leading edge of the prop is experiencing airflow, which should be a smaller cross section. Except that it's also doing "work". I'm sure that there's sufficient experiential data about the behavior and impact of windmilling props to confirm that it's worse than a stopped one, but does anyone have a clear aerodynamic explanation of why it should be so?

Think of how much energy you would use, or work you would do, to spin the propeller at windmilling speed using your arm. That is the same amount of energy lost by the glider, in the form of drag, of the windmilling prop.

Mike

On Wednesday, October 11, 2023 at 4:46:30 PM UTC-7, Mike Reid wrote:
> On Wednesday, October 11, 2023 at 8:19:01 AM UTC-8, Doug Bailey wrote:
> > On Wednesday, October 11, 2023 at 7:08:13 AM UTC-7, bumper wrote:
> > > > The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!
> > > Another major factor is whether the prop is windmilling or stopped. A windmilling prop adds almost the flat plate surface of its swept area. A large drag reduction is had by stopping to prop, and of course even more by stowing it. If one can't stop it due to a broken belt or whatever, they laying in down nets a large gain in L/D over a windmilling prop.
> > >
> > > bumper
> > That's a really interesting observation, and simultanously intuitive, and not to my mind. If the prop is stopped, then you have a stalled plate the shape of a prop in the airflow - so I guess the impact of that is pretty obvious. But when the prop is windmilling, the leading edge of the prop is experiencing airflow, which should be a smaller cross section. Except that it's also doing "work". I'm sure that there's sufficient experiential data about the behavior and impact of windmilling props to confirm that it's worse than a stopped one, but does anyone have a clear aerodynamic explanation of why it should be so?
> Think of how much energy you would use, or work you would do, to spin the propeller at windmilling speed using your arm. That is the same amount of energy lost by the glider, in the form of drag, of the windmilling prop.
>
> Mike

The last paragraph of the paper that Dave found says: "The main goal of this investigation was simply to determine whether a stationary or a windmilling propeller has more drag. The answer is complicatedly simple: it depends. It is clear that it depends on the pitch and length of the propeller, and it is probably independent of the wind velocity. A crossover point was discovered where the drag forces for the windmilling and stationary states were the same. This crossover point is also dependent on the pitch, the length, and probably independent of the wind velocity. "

So I guess it's not such a cut-and-dried outcome at all.

On Wednesday, October 11, 2023 at 2:55:40 PM UTC-7, youngbl...@gmail.com wrote:
> On Wednesday, October 11, 2023 at 1:21:56 PM UTC-4, Dave Nadler wrote:
> > On Wednesday, October 11, 2023 at 12:19:01 PM UTC-4, Doug Bailey wrote:
> > > ...I'm sure that there's sufficient experiential data about the behavior and
> > > impact of windmilling props to confirm that it's worse than a stopped one...
> > https://www.peter2000.co.uk/aviation/misc/prop.pdf
> Seems like these motorgliders are falling out of the sky like raindrops in the Everglades. Us Purist really don't have that wind milling prop problem and we make it home for dinner. After all the post about how much safer a motorglider is and there seems to be a rash of accidents, can someone please explain this, Eric, I anxiously await your reply. OBTP
Who told you a motorglider was safer? It wasn't me, Dave Nadler, Jon Fitch, or anyone else here; in fact, it was you that argues getting a tow was tougher than a self launch. In fact, you have routinely dismissed motorglider pilots for taking the easy way, instead of taking chances as the "superior" towed pilots do.

So, to repeat myself: motorgliders are more complex, they require more awareness of the area around them, and the motor provides the means for the pilot to place himself in situations that are not easily obtainable by the towed pilot, if at all. For a most pilots, there is no reason believe they improve the pilot's safety. Please, please, read my Guide to self-launcher operation, so I do not have to lecture you from it, chapter by chapter.

Please, please, read my Guide to self-launcher operation, so I do not have to lecture you from it, chapter by chapter.

Eric- Give up! You and all the Saints and Apostles are incapable of talking any sense into OBTP. He is fundamentally a stubborn old man who believes his own crap.

On Thursday, October 12, 2023 at 5:57:19 AM UTC-7, Mark628CA wrote:
> Please, please, read my Guide to self-launcher operation, so I do not have to lecture you from it, chapter by chapter.
> Eric- Give up! You and all the Saints and Apostles are incapable of talking any sense into OBTP. He is fundamentally a stubborn old man who believes his own crap.
@Mark - You are probably correct, but my remarks to Old Bob are mostly intended for other pilots that might be misled by his comments. In this particular case, I'm concerned some pilots might accept his comment that it's generally accepted motorgliders are safer than towed glider. I doubt Old Bob will read the Guide, but it might encourage a couple other pilots to do so.

On Wednesday, October 11, 2023 at 4:46:30 PM UTC-7, Mike Reid wrote:
> On Wednesday, October 11, 2023 at 8:19:01 AM UTC-8, Doug Bailey wrote:
> > On Wednesday, October 11, 2023 at 7:08:13 AM UTC-7, bumper wrote:
> > > > The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!
> > > Another major factor is whether the prop is windmilling or stopped. A windmilling prop adds almost the flat plate surface of its swept area. A large drag reduction is had by stopping to prop, and of course even more by stowing it. If one can't stop it due to a broken belt or whatever, they laying in down nets a large gain in L/D over a windmilling prop.
> > >
> > > bumper
> > That's a really interesting observation, and simultaneously intuitive, and not to my mind. If the prop is stopped, then you have a stalled plate the shape of a prop in the airflow - so I guess the impact of that is pretty obvious. But when the prop is windmilling, the leading edge of the prop is experiencing airflow, which should be a smaller cross section. Except that it's also doing "work". I'm sure that there's sufficient experiential data about the behavior and impact of windmilling props to confirm that it's worse than a stopped one, but does anyone have a clear aerodynamic explanation of why it should be so?
> Think of how much energy you would use, or work you would do, to spin the propeller at windmilling speed using your arm. That is the same amount of energy lost by the glider, in the form of drag, of the windmilling prop.
>
> Mike
@Mike Reid - I like this way of thinking about it. For the glider being discussed here (the ASH26E), the only time the propeller is likely to windmill is 5-10 seconds after it's shut down, or if the belt breaks (very, very rare). With a broken belt, I'd call it "freewheeling" instead of "windmilling", because the only drag on it is the prop shaft bearing friction. That's quite small, so while it'd spin quickly, it would produce very little drag. In airplanes, the windmilling propeller is driving the engine, which produces a lot of drag, and I'd expect stopping the prop would reduce that drag.

On Thursday, October 12, 2023 at 7:42:28 AM UTC-7, Eric Greenwell wrote:
> On Wednesday, October 11, 2023 at 4:46:30 PM UTC-7, Mike Reid wrote:
> > On Wednesday, October 11, 2023 at 8:19:01 AM UTC-8, Doug Bailey wrote:
> > > On Wednesday, October 11, 2023 at 7:08:13 AM UTC-7, bumper wrote:
> > > > > The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!
> > > > Another major factor is whether the prop is windmilling or stopped. A windmilling prop adds almost the flat plate surface of its swept area. A large drag reduction is had by stopping to prop, and of course even more by stowing it. If one can't stop it due to a broken belt or whatever, they laying in down nets a large gain in L/D over a windmilling prop.
> > > >
> > > > bumper
> > > That's a really interesting observation, and simultaneously intuitive, and not to my mind. If the prop is stopped, then you have a stalled plate the shape of a prop in the airflow - so I guess the impact of that is pretty obvious. But when the prop is windmilling, the leading edge of the prop is experiencing airflow, which should be a smaller cross section. Except that it's also doing "work". I'm sure that there's sufficient experiential data about the behavior and impact of windmilling props to confirm that it's worse than a stopped one, but does anyone have a clear aerodynamic explanation of why it should be so?
> > Think of how much energy you would use, or work you would do, to spin the propeller at windmilling speed using your arm. That is the same amount of energy lost by the glider, in the form of drag, of the windmilling prop.
> >
> > Mike
> @Mike Reid - I like this way of thinking about it. For the glider being discussed here (the ASH26E), the only time the propeller is likely to windmill is 5-10 seconds after it's shut down, or if the belt breaks (very, very rare). With a broken belt, I'd call it "freewheeling" instead of "windmilling", because the only drag on it is the prop shaft bearing friction. That's quite small, so while it'd spin quickly, it would produce very little drag.. In airplanes, the windmilling propeller is driving the engine, which produces a lot of drag, and I'd expect stopping the prop would reduce that drag..

>but does anyone have a clear aerodynamic explanation of why it should be so?
S. F. Hoerner, "Fluid Dynamic Drag", pages 13-21, 22.

The point is a 11:1 glide ratio was not enough to get him to a landable field. That is why I am saying 10:1 with the engine out has a safe margin for normal conditions. You are saying the best glide is better than this, but who would want to use the best glide in practice for staying safe. This is like setting the MC at 0.0. I don't believe most people practice this situation.
> > Buzz Graves
> The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!

On Thursday, October 12, 2023 at 10:56:38 AM UTC-7, BG wrote:
> The point is a 11:1 glide ratio was not enough to get him to a landable field. That is why I am saying 10:1 with the engine out has a safe margin for normal conditions. You are saying the best glide is better than this, but who would want to use the best glide in practice for staying safe. This is like setting the MC at 0.0. I don't believe most people practice this situation.
> > > Buzz Graves
> > The glider's flight trace from an IGC file does not show the still air glide ratio, as wind and sink can change the achieved glide ratio over the ground. The glide ratio of the ASH26E with the mast up and gear down is well known to owners, and it is in the 18-20:1 range. A 11:1 ratio would truly be the "plummet mode" Dave sometimes refers to, and us 26E owners would definitely notice it!
It appears we were talking about different things. My comments were about a factual matter; ie, the measured glide ratio of an ASH26E with the mast up.. I am in total agreement you should not bet your safety on achieving that glide ratio, especially at 900' AGL with trees ahead! That might be high enough to attempt a restart IF the pilot was on the downwind leg for a good field, already configured for landing.

On Wednesday, October 11, 2023 at 8:35:30 PM UTC-7, Eric Greenwell wrote:
> On Wednesday, October 11, 2023 at 2:55:40 PM UTC-7, youngbl...@gmail.com wrote:
> > On Wednesday, October 11, 2023 at 1:21:56 PM UTC-4, Dave Nadler wrote:
> > > On Wednesday, October 11, 2023 at 12:19:01 PM UTC-4, Doug Bailey wrote:
> > > > ...I'm sure that there's sufficient experiential data about the behavior and
> > > > impact of windmilling props to confirm that it's worse than a stopped one...
> > > https://www.peter2000.co.uk/aviation/misc/prop.pdf
> > Seems like these motorgliders are falling out of the sky like raindrops in the Everglades. Us Purist really don't have that wind milling prop problem and we make it home for dinner. After all the post about how much safer a motorglider is and there seems to be a rash of accidents, can someone please explain this, Eric, I anxiously await your reply. OBTP
> Who told you a motorglider was safer? It wasn't me, Dave Nadler, Jon Fitch, or anyone else here; in fact, it was you that argues getting a tow was tougher than a self launch. In fact, you have routinely dismissed motorglider pilots for taking the easy way, instead of taking chances as the "superior" towed pilots do.
>
> So, to repeat myself: motorgliders are more complex, they require more awareness of the area around them, and the motor provides the means for the pilot to place himself in situations that are not easily obtainable by the towed pilot, if at all. For a most pilots, there is no reason believe they improve the pilot's safety. Please, please, read my Guide to self-launcher operation, so I do not have to lecture you from it, chapter by chapter.
At least on the landing phase, motorgliders need be no safer or less safe than a towed glider. You just need to keep your finger away from the start button. That temptation has been the downfall of a few motorglider pilots. If you don't trust yourself or your judgement, best not to have that temptation.

On spinning vs. still props, there have been several tests of this over the years, and the result is always "it depends". Not just on the things already mentioned, but how much torque the prop is absorbing. Best to stop it and fold it back, or if you weren't sure of your landing, don't get it out to begin with.