Kawa rough landing?

Dave Nadler wrote on 9/18/2019 7:43 AM:
On Wednesday, September 18, 2019 at 9:07:32 AM UTC-4, Eric Greenwell wrote:
...is many motorgliders do not "plummet" or become less controllable
because the mast is up

And, many DO plummet, with reduced control authority.
It is highly dependent on what kind of glider!
Don't assume...

That's why I recommend owners try at least one airport landing with the mast up,
and engine stopped, so they know what to expect if it happens to them. The 26E,
with the gear out and mast up, reminds me of landing a Blanik.

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?

--
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 Wednesday, September 18, 2019 at 3:16:37 PM UTC-7, Eric Greenwell wrote:
Dave Nadler wrote on 9/18/2019 7:43 AM:
On Wednesday, September 18, 2019 at 9:07:32 AM UTC-4, Eric Greenwell wrote:
...is many motorgliders do not "plummet" or become less controllable
because the mast is up

And, many DO plummet, with reduced control authority.
It is highly dependent on what kind of glider!
Don't assume...

That's why I recommend owners try at least one airport landing with the mast up,
and engine stopped, so they know what to expect if it happens to them. The 26E,
with the gear out and mast up, reminds me of landing a Blanik.

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?

--
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
,

This is true. I fly a DG800 and with the mask out the sink rate is 4-5 knots, so my glide ratio is roughly 4-5 less. Air starts are typically on down wind to a know good field with in a 10:1 glide. If I am over uncharted territory, I will initiate the restart at a much higher altitude, even this adds extra risk if the engine won't start and I can not retract. The manual clearly states that landing with the mask out can easily lead to a hard landing, especially if any spoilers are deployed, they recommend no spoilers and extra airspeed needed to overcome the added sink rate on touch down. If you were about to land in one of the most difficult fields in your career, why would you choose to make it extra complicated with a engine mask out.. That is if you were not still being wishful it would miraculously start working. I feel this is a critical moment every MG pilot will find themselves one day. So over unlandable or very difficult terrain the plan of action to relight needs to happen at a much higher altitude that will allow retracting if things don't work. With the mask out most gliders performance degrades and requires extra airspeed to reliably reduce the extra sink rate on touch down. We all make mistakes and learn from them. A glider with a mask out in a very difficult outlanding is not good planning, especially if the mask system is working and the engine is not. Those that don't fly a MG think we have some advantage, when indeed we need to terminate our flight as a glider at a higher altitude. If you want to roll the dice and try to restart from a low altitude, if it works great which most of the time it would, but when it does not you are disadvantaged and add plenty of risk. Of my friends who fly a similar glider, one did the right thing in a difficult landing in a known good short field deep in the woods, rather than try a restart he landed. The other landing short with his mask out hanging in the trees on another day.

BG

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

Andreas Maurer wrote on 9/19/2019 12:11 PM:
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.

That's one, perhaps, but 443 fpm doesn't seem like "plummeting" to me. I'm
surprised it's so poor mast up, as I've read the PIK20E is 15:1 with the mast up,
and that's only a 15 meter glider with the engine on the mast, unlike the buried
engine in the Arcus M. How does mast up compare to half or full spoiler, and is
that measured with the gear down?

Here's another data point: the last time I flew my ASH26E, I stopped the engine
while thermalling, but did not lower the mast. The glider continued to climb at a
reduced rate in the thermal. Note that the mast is always left half extended to
cool for several minutes after an engine run, and the thermal climb is not
noticeably improved when the mast is finally fully retracted. So, NO plummet mode
on the 26E, and really don't think it's that much different from an 18 M Ventus or DG.


--
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

Eric, thanks for the response. While you have been flying relatively high performance machines, I have chosen to go a different route. The challenge for me is doing more with less. I fly a very low performance bird and have been pursuing the goal of setting records and making long distance flights in a 22/1 L/D machine.

To successfully do this type of flying requires a completely different set of soaring skills than the ones you use. Namely, I have to become "comfortable" with multiple low saves on virtually every record flight due to the fact that I do not have the lift-finding-reach that comes with higher performance. As a direct corrolary, I have to also become very proficient in the evaluation and utilization of every available scrap of landable terrain. I don't have the luxury of many others who have the "wing power" to cross large tracts of ground considered unlamdable. For me to reach my goals, I have to intimately know the skills I mentioned previously.

While my situation would be considered extreme by many, it is not. It is simply returning to the type of flying that the soaring pioneers of the 50's and 60's did. But now it can be done with the benefits of modern "high performance" electronic aids such as flight computers, gps, active real time wx, and active tracking, all of which increase the safety and efficiency factors to points our pioneers could only have dreamt of.

All that being said, the skills and the repetitous practice needed to gain those skills (things the successfull pioneers all had) are things that, in my oinion, need to be brought back into vogue. In todays day and age, there is entirely too much dependance upon performance and motorized aid to save a fellow. Proof of this is clearly seen in the rash of fatalities we are seeing.

It is well, necessary, and good to have personal risk standards. I also have them. But what does one do when they find themselves in a pinch, when they find that they have inadvertantly put their tail in a crack. This is what is happening. Sure there are probably a few guys who are simply flying hell bent for leather and as a consequence getting themselves killed. But I think the vast majority of the fatalities and serious injury accidents we are seen are more of the former case, where guys are simply slightly over extended, and finding themselves in a predicament, have no idea how to handle it.

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.

Hard data.Â* That what this site needs more of.Â* Thanks, Mark.

On 9/21/2019 7:06 AM, 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.

--
Dan, 5J

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). One ASH26e pilot reported a glide of 17:1 with prop out, and the 26e has fairly long engine bay doors. I have landed the 26e with the prop out and it was uneventful. I have also landed the DG400 uneventfully with the prop out; the one thing to remember is that you don't have the same glide that you do with the engine stowed, so don't make big patterns. I suspect that is what happened to the two cases that were cited. I have also made a simulated engine failure landing in a C152, and its glide was significantly worse (had to go straight for the runway after a 135 degree turn).

Tom

2G wrote on 9/21/2019 1:30 PM:
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). One ASH26e pilot reported a glide of 17:1 with prop out, and the 26e has fairly long engine bay doors. I have landed the 26e with the prop out and it was uneventful. I have also landed the DG400 uneventfully with the prop out; the one thing to remember is that you don't have the same glide that you do with the engine stowed, so don't make big patterns. I suspect that is what happened to the two cases that were cited. I have also made a simulated engine failure landing in a C152, and its glide was significantly worse (had to go straight for the runway after a 135 degree turn).

Was the 13:1 measured with gear down? With the propeller stopped? In the flap
position for best glide?


I agree with Tom. It may be counter-intuitive that the drag of a mast is
relatively small, but low speeds, the wing is generally the biggest drag producer,
not stuff sticking out in the wind.


As I mentioned earlier, 26E owners spend 2 to 5 minutes cooling the engine after
stopping it. The mast is lowered to about a 30 degree angle to the fuselage, which
holds the doors completely open. And yet, we can thermal effectively, and when we
finally stow the mast, we don't notice any improvement in climb rate. We're not
fooling ourselves on this - we have thermalled with other gliders while the mast
is in the cooling position, and still climb with them.

Open doors on 26E make very little drag at 50-55 knots, and I suspect that is also
true of the Arcus M. After all, would SH design a glider with doors that reduce
the climb rate by 300 fpm?

--
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

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.