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My 9A Became a Glider Today

339A

339A

Well Known Member
Intentionally that is…. Well this is something I have wanted to do for a while now. It was an absolutely perfect Colorado day, wind calm, about 45 degrees out, who needs to go to work on a day like this? It’s a far better day for flying than working. Off to the airport I go with a plan in mind.

A friend sent me this video of an RV4 doing a power off descent and landing from about 8500 feet. This is something I’ve contemplated and decided it was time to do. For my purpose today I would fly over to Limon (LIC) and perform my engine out glide test. Upon arriving over the airport at 9500 feet, I slowed down to slow flight speed and practiced. The 9A is pretty easy to handle at 70 MPH, a few minutes of this and I was ready. Everything was good so I decided to pull the red knob and throttle all the way back. The engine RPM finally dropped off and the EIS was not a happy camper, as all manner of alarms came in. The engine continued to windmill and I found this to be annoying. Keeping a close eye on my airspeed I pulled back on the stick in an attempt to stop the prop (Catto three bladed fixed). It finally stopped and stayed that way. I then tried various airspeeds and recorded my vertical descent speeds. These tests were done with no flaps so I’m sure the numbers will change when flaps are added.

70 MPH equals 400 FPM
75 MPH equals 500 FPM
80 MPH equals 600 FPM
85 MPH equals 750 FPM
90 MPH equals 1000 FPM

About 2000 feet AGL I pushed the throttle and mixture back in, mags on and hit the starter. She fired right up and I climbed back to 9500 and did it all over again. I did this three times with the same results each time. My next step will be to actually dead stick the airplane. But I was quite happy with my efforts for the day. It’s amazing how much different things sound once the engine is off. At 70 MPH it was fairly quiet, but as the speed increases the wind noise goes up significantly. Something we just don’t normally hear with the engine running.

I’m glad I did this, and now I have some real experience/numbers if the engine does quit. Anyone who is comfortable flying their plane should give this a try and find out some useful numbers. The hardest part is going to be discerning at what point to turn for the field. In my attempts today I would have been quite high on final, but I plan to work on that and come up with a better technique for making the runway/field from about 1000 feet.
 
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Excellent! This makes a nice polar for your new RV-9G. Interestingly, your best L/D came at your minimum sink - L/D of 15.4 at 70mph and 400 fpm. 400 fpm and L/D of 15 means you have a lot of time to figure out what's wrong and pick landing spots if the engine quits at 9500 without warning.

Since your measured max L/D was the slowest of your data points, it suggests that you may not have found the actual best L/D. Normally you will see sink continue to go down but L/D increase as speed gets close to stall. ANy chance you can give us some data points at 60 and 65?

And you're right, the wind noise changes a lot with speed. In a glider, you have multiple ways of avoiding the stall - nose below the horizon, enough wind noise and ASI. If you point the nose below the horizon, you will find it very, very hard to stall.

Now, the power pilot part of me thinks this can't have been good for your engine.... Did your CHTs drop off as you were doing the powered slow flight? And as for watching the airspeed drop off as you're getting the prop to stop, well, so what if it stalls? It's just like a normal stall recovery. The wing doesn't know that the engine is off and will recover just like after a power-off stall without adding power.

TODR
 
Thanks for the input Doug. I was really amazed how much time I had. It felt like I could stay up there all day, although I know that's not true ;) At 70 MPH everything seemed so slow.

I did slow down to 65 once, but didn't keep it there long enough to stabilize and record numbers. I will do that next time. I didn't want to get into the stall today with the engine off as I wasn't sure it would re-start. Being as this was my first time, the excitement of the prop not turning was all the fun I needed. I will get better info on the next tests. I'm sure it won't be so exciting the next time. :cool:

As for the CHT's I do rememeber getting the C-RATE alarm from the EIS (set at 80) but it was not on my list of things to pay attention to. I sometimes see this if I slow down too quickly, but not very often.

This is really a lot of fun once you get over the amazement of the engine not turning. My whole purpose in this was to get a "feel" for what would happen if the engine did quit and how much time I would have.

I am headed to Texas next week with the plane for a month long project. Looks like I'll be staying at your airport, ADS, courtesy of someone on this list.

Regards,
 
Great fun isn't it. I did this testing too, in a very similar fashion except I didn't have the ... to stop the prop. I can say from looking at your numbers that the C/S prop that I have results in a MUCH greater sink rate.
 
Scott,

Keep us posted of further testing. 2 years ago while I was out at LOE I talked my original flight instructor (now A10 pilot) into doing an engine off test with me. I just wanted the experience so it wouldn't be a complete shock if it happened for real. (Just like spin training..) We did not take the time to document our results, it was more for the experience. Certainly was an interesting sensation flying with the prop stopped.


339A said:
Intentionally that is?. Well this is something I have wanted to do for a while now. It was an absolutely perfect Colorado day, wind calm, about 45 degrees out, who needs to go to work on a day like this? It?s a far better day for flying than working. Off to the airport I go with a plan in mind.

A friend sent me this video of an RV4 doing a power off descent and landing from about 8500 feet. This is something I?ve contemplated and decided it was time to do. For my purpose today I would fly over to Limon (LIC) and perform my engine out glide test. Upon arriving over the airport at 9500 feet, I slowed down to slow flight speed and practiced. The 9A is pretty easy to handle at 70 MPH, a few minutes of this and I was ready. Everything was good so I decided to pull the red knob and throttle all the way back. The engine RPM finally dropped off and the EIS was not a happy camper, as all manner of alarms came in. The engine continued to windmill and I found this to be annoying. Keeping a close eye on my airspeed I pulled back on the stick in an attempt to stop the prop (Catto three bladed fixed). It finally stopped and stayed that way. I then tried various airspeeds and recorded my vertical descent speeds. These tests were done with no flaps so I?m sure the numbers will change when flaps are added.

70 MPH equals 400 FPM
75 MPH equals 500 FPM
80 MPH equals 600 FPM
85 MPH equals 750 FPM
90 MPH equals 1000 FPM

About 2000 feet AGL I pushed the throttle and mixture back in, mags on and hit the starter. She fired right up and I climbed back to 9500 and did it all over again. I did this three times with the same results each time. My next step will be to actually dead stick the airplane. But I was quite happy with my efforts for the day. It?s amazing how much different things sound once the engine is off. At 70 MPH it was fairly quiet, but as the speed increases the wind noise goes up significantly. Something we just don?t normally hear with the engine running.

I?m glad I did this, and now I have some real experience/numbers if the engine does quit. Anyone who is comfortable flying their plane should give this a try and find out some useful numbers. The hardest part is going to be discerning at what point to turn for the field. In my attempts today I would have been quite high on final, but I plan to work on that and come up with a better technique for making the runway/field from about 1000 feet.
Click to expand...
 
Some Quibbles and Comparison

the_other_dougreeves said:
... Interestingly, your best L/D came at your minimum sink - L/D of 15.4 at 70mph and 400 fpm. 400 fpm and L/D of 15 ...
Since your measured max L/D was the slowest of your data points, it suggests that you may not have found the actual best L/D. Normally you will see sink continue to go down but L/D increase as speed gets close to stall. ANy chance you can give us some data points at 60 and 65?
...
TODR
Click to expand...
Maybe we are using different terms, but the best or max L/D speed will always have a greater sink rate than the minimum sink speed by almost exactly 14% and the CAS difference between those speeds will be: MinimumSink x 1.316 = Max L/D. The numbers do suggest that the minimum sink speed would have been even slower (perhaps as low as 54). It is important to remember that the best glide will not be at the least sink speed but 1.316x faster.

The best way I know to determine best glide (max L/D) speed is with the Garmin handheld displaying the glide ratio field and this can be done even with the power on to reduce the sink rate. The speed at which the Garmin says the ratio is highest is the IAS at which (for that weight) the reported ratio is highest. Power changes with AOA/IAS held constant will not change the result, only the ratio. The same speed will be best. Of course, a constant wind is needed so heading must be held. The actual ratio reported by the Garmin is not relevant, only that the highest ratio tells you the best speed. Once you know the best L/D speed you can compute the minimum sink speed (assuming the IAS error from CAS does not vary much). It's likely these speeds won't be at 5 mph intervals.

CAFE's 9A had a reported glide ratio of 12 at 95 mph and a minimum sink speed of 82, stalling at 49. I don't think their speeds conform sufficiently to the known mathematical "facts", but it's interesting to note how different they are from this report. It's useful to remember that IAS and CAS can be very different, especially at high angles of attack.
http://cafefoundation.org/v2/pdf_apr/rv-9a.pdf
 
The URL you posted for the CAFE document is not public and at least 'I' cannot access it, probably most others also cannot access it. Would it be possible to post a public link or perhaps make the document available via some other means? I don't know what if any copyright issues might be involved, according to their URL, the Cafe Foundation is a non-profit organization after all.

Thanks!
 
I had a c150 that used to engage in engine out glide contest with a luscombe until the 1st annual after that, I discovered 2 cracked cylinders. This put an end to my engine out experiments. It is an expensive test to do.
 
scard said:
Great fun isn't it. I did this testing too, in a very similar fashion except I didn't have the ... to stop the prop. I can say from looking at your numbers that the C/S prop that I have results in a MUCH greater sink rate.
Click to expand...

Actually, I am pretty sure that any prop (fixed pitch or constant speed) produces more drag if left turning versus being stopped.

It would be interesting if Scott got data with the prop windmilling and stopped.
 
rvbuilder2002 said:
Actually, I am pretty sure that any prop (fixed pitch or constant speed) produces more drag if left turning versus being stopped...
Click to expand...
I did this test and the glide was certainly better with the prop stopped, but it wasn't a huge difference with my O-360 and Sensenich fixed pitch. I decided you would have to be real high for it to be worth it to slow down enough to stop the prop.
 
Try this link to CAFE

647jc said:
The URL you posted for the CAFE document is not public and at least 'I' cannot access it, probably most others also cannot access it. Would it be possible to post a public link or perhaps make the document available via some other means? I don't know what if any copyright issues might be involved, according to their URL, the Cafe Foundation is a non-profit organization after all.

Thanks!
Click to expand...

http://cafefoundation.org/v2/research_aprs.php
Find the 9A in their menu.
I don't know why it does what it does when you try to go there directly. I have had the same problem.
 
Scott,
You might want to also try; dead engine, prop windmilling and throttle FULL IN and compare this to the prop stopped sink rates??

Fin
9A
 
Some answers

I'm not an aeronautical engineer, but I do stay at a lot of Holiday Inns. :p To answer Scott's question I did not get any data with the prop windmilling. With the engine stopped and the prop windmilling there was a noticable shake which I did not like. It was not severe at all, I just found it annoying and once I got the prop stopped it was quite peaceful.

I wanted to get results with the prop stopped, as with my limited aeronautical understanding, this should be the least amount of drag on the airframe.

As for shock cooling here is a good article on the subject (via AV web) by Kas Thomas.
 
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Finley Atherton said:
Scott,
You might want to also try; dead engine, prop windmilling and throttle FULL IN and compare this to the prop stopped sink rates??

Fin
9A
Click to expand...

Yep, did it. Throttle full in, prop full out, vice-versa. The engineering data (that I choose not to share) I collected confirms the expectations, but the reality of flight, attempting to maintain the best case is nearly absurd given the circumstances observed (turbulence, winds, etc.).
I did a lot of testing and recording numbers with an O-320, C/S prop, -9A and I concluded, and the instructions to Tanya (primary solo pilot and most prized companion) are, "fly what you've got with eyes out the window, in reality, you can be sure to make X miles for X feet altitude at 70-80 kts." It seems that for some, knowing what X miles looks like out the window is the trick if you intend to land on something that isn't right beneath you.

In the end, it is all academic, and I hope to be ready to fly the insurance company's airplane to the crash site when the time comes. Really, this is a daily exercise. The problem is that I really am an "Academic". :).
 
I did about the same thing during my 40 hours. While I didn't record the numbers with a windmilling prop, I got lower sink rates with the prop stopped. IIFC, 400 fpm was about the minimum and the test was done at 1400 lb. My minimum sink came just below 70 mph and did increase quite a bit at 60. I would use 70 if gliding downwind and 85 or so penetrating into the wind. Given anything over about 3000 AGL, I would stop the prop if I couldn't get a restart.

I never tried a diving restart and don't know at what speed the prop would turn without the starter, but I would expect it would at some speed. I did always get my CHT's down before killing the engine. And you are right; it is quiet and sort of peaceful. Not as much so as a sailplane, however.

Just speculation here, but I would suspect that the stopped prop may be better for the engine. This ends cooling on the inside of the cylinder which I would think would slow "shock cooling." I would also suspect cylinder wear might be lower as pumping cold air through the cylinder isn't a normal function except at startup, long known to be the time of highest cylinder wear. I doubt if this really matters, but it is fun to actually see the prop out there. Especially when you know you can turn it into a blur again!

Bob Kelly
 
Pretty much kills the theory of shock cooling.
Click to expand...
I am curious about this comment :confused:

I have never understood "Shock Cooling" to mean the engine will not restart / pick up... just that it does damage to the engine over the longer term... and every time you "shock cool" it you do more damage.

I for one am glad that these test results are being posted here - saves me trashing my engine to get them :D

Sorry to be a bore, but I might be interested to know what the FAA and your Insurance company would say should the engine not restart, and the ensuring forced landing was unfortunately unsuccessful? Or is it part of the 40hr Phase 1 schedule you have to do in the USA? I am pretty sure I know what our LAA/CAA and AAIB would have to say :eek:

Apart from formal Flight Testing e.g. for Certification, I am unaware of anyone shutting engines down on singles intentionally with no fault/failure present...

As I said, sorry to be a bore.. but doing this seems strange - but publically advertising on it on a public forum :confused: Apart form what it does to the resale value of the aircraft above where this practice has been carried out :rolleyes:

Andy Hill
RV-8 G-HILZ
 
I have conditioned my self that in the event of a power failure at cruise speed, the first thing on the emergency checklist is to zoom climb and convert the speed in excess of best glide, to altitude. At the end of the zoom I will let the speed slow enough for the prop to stop, then pitch over and accelerate to best glide speed. This pitch over will lose some of the gained altitude but it will still produce a net gain over what it would have been. Doing this can easily net another 1000 ft +. During the 20 seconds or so of the zoom climb, I am running through the remaining parts of the power loss checklist. By the time I get to the apogee of the zoom I will have determined whether this is really going to be a forced landing or not

If I am over more hospitable terrain or I am already pretty low, I would skip stopping the prop. The difference in glide distance or time until landing would be very slight if already at low altitude, the time should be spent preparing to land.

I do agree with Scott...fly the airplane to the landing that gives the best possible outcome for the occupants...forget the airplane. But out here in the western third of the U.S., there are times when having the most glide distance possible, would likely have an effect on what the forced landing outcome would be. I try to avoid situations like this but sometimes it is just not possible.

This is my personal plan, It is not for everyone. The main point I want to make with this post is..."Do you have a plan?"
You need to have already decided what you will do in a situation such as an engine failure, and then just do it.
 
Get some data before you decide on shock cooling I suggest....

339A said:
As for shock cooling here is a good article on the subject (via AV web) by Kas Thomas.
Click to expand...

In that article he says " "Scientific proof" is perhaps a poor choice of words. What I'm simply trying to say is, the hard evidence is scanty. I know of no fleet studies on this subject.

If anyone is interested, there IS a small fleet study of 5 aircraft about 65000 aero tows or more, and 28 cyls in the UK. I find it easier to use that as data than one guy who stopped his prop!

If it interests you I put a post once before that will get you to the study. Its here: http://www.vansairforce.com/community/showpost.php?p=175233&postcount=9
 
Andy Hill said:
I am curious about this comment :confused:

I have never understood "Shock Cooling" to mean the engine will not restart / pick up... just that it does damage to the engine over the longer term... and every time you "shock cool" it you do more damage.

I for one am glad that these test results are being posted here - saves me trashing my engine to get them :D

Sorry to be a bore, but I might be interested to know what the FAA and your Insurance company would say should the engine not restart, and the ensuring forced landing was unfortunately unsuccessful? Or is it part of the 40hr Phase 1 schedule you have to do in the USA? I am pretty sure I know what our LAA/CAA and AAIB would have to say :eek:

Apart from formal Flight Testing e.g. for Certification, I am unaware of anyone shutting engines down on singles intentionally with no fault/failure present...

As I said, sorry to be a bore.. but doing this seems strange - but publically advertising on it on a public forum :confused: Apart form what it does to the resale value of the aircraft above where this practice has been carried out :rolleyes:

Andy Hill
RV-8 G-HILZ
Click to expand...
Andy,
It's interesting that you would thank someone for doing some testing so that you didn't have to subject your engine to the same conditions, but then criticize them for doing it...:eek:

Since RV's are not certificated airplanes with an associated Pilots Operating Handbook to look up such information, I don't think the FAA or an insurance company would make a big issue of it if it was being done during phase 1 for a specific purpose. Certainly, the NTSB report would specify that the pilot choosing to purposely shut down the engine was a contributing factor, but the actual outcome of the landing probably would have occurred with any particular pilot at the controls, whether he purposely cause the engine stoppage or it was accidental.

One good point though...when purposely shutting down an engine, the pilot should be fully prepared to execute a power off landing. Consequently, choosing to do it over an airport with a long (preferably more than one) runway is a good decision.
 
stopping the prop

My RV7 is not flying yet so I am not speaking from experience but, it would seem to me that when making a landing with the engine turned off you would want to have the prop stopped prior to final approach. This is because the short wing design will have a lot more drag (and relatively steep approach) with the prop turning compared to not turning. So when approaching to land with prop turning, you've got your touchdown spot identified, your speed drops for the flare, then unexpectedly the prop stops, drag goes way down, speed picks up, your raise the nose to control speed and overshoot your touchdown point. This may be significant if your looking at a short stretch of favorable road or small field, parking lot etc.

So, getting the prop stopped should be attempted prior to final approach and once the decision has been made not to restart? This also provides a better chance of saving the engine and prop by minimizing prop strike.

What says the experts who have practical experience?

My .o2 cents.

Bevan
 
Bevan said:
...So, getting the prop stopped should be attempted prior to final approach and once the decision has been made not to restart? This also provides a better chance of saving the engine and prop by minimizing prop strike.

What says the experts who have practical experience?

My .o2 cents.

Bevan
Click to expand...
Well, I'm not an expert, but when I was doing engine out testing, I did make one dead-engine landing starting with the prop turning. Somewhere on final the prop stopped and it was a complete non-issue. As I noted before, in my airplane (fixed pitch) the performance difference with the prop stopped in not much different than with the prop turning. The only unusual thing about the landing was that the deceleration in the flare was noticeably faster compared to an engine-running landing. I think things would be considerably different with a constant speed prop.
 
An Ounce of Prevention ...

... is worth a pound of cure. Definition: A little precaution before a crisis occurs is preferable to a lot of fixing up afterward.

As I said, sorry to be a bore..
Click to expand...

Some of us just can't help it, I guess ... :rolleyes:
 
Some time ago, after doing some dead engine glides in my 9A with a Hartzell C/S prop, I decided that stopping the prop to extend the glide was not really practical. The first problem was stopping the prop. Initially I tried with the prop full coarse and I gave up at 49 Kts IAS. With the prop full fine it stopped at 51 kts. So to stop the prop I needed to put the flaps down to prevent stalling. In a real engine out emergency I would not really want to be messing around not far from stall speed with the flaps down and sinking very rapidly and then bringing the flaps back up and increasing speed to obtain the best glide. In a real engine failure, if time permits I would naturally attempt to restart the engine with the starter and this would have the prop windmilling again! I also found that the sink rate was slightly higher with the prop stopped (full fine) than with the prop windmilling and the prop control full coarse.

Fin
9A
 
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hevansrv7a said:
Maybe we are using different terms, but the best or max L/D speed will always have a greater sink rate than the minimum sink speed by almost exactly 14% and the CAS difference between those speeds will be: MinimumSink x 1.316 = Max L/D. The numbers do suggest that the minimum sink speed would have been even slower (perhaps as low as 54). It is important to remember that the best glide will not be at the least sink speed but 1.316x faster.
Click to expand...

Yes; MAX L/D occurs with higher sink rates than the minimum sink rate.

Airspeed at minimum sink rate will be lower than L/D MAX. Actual L/D at minimum sink airspeed will be less than L/D MAX.

TODR
 
Emergency landing pattern

It always seem strange to me during these discussions that there is never a discussion about emergency landing patterns. My military flight instructor experience (Navy) saw us spending much of our primary flight intruction time teaching an emergency landing pattern.

This pattern consisted of arriving over your intended point of landing heading in the direction of intended landing at best glide airspeed (Hi Key) with about 2500' altitude AGL. From there you performed a constant AOB 360 degree turn to final. Flaps came down when the field was made.

This pattern gives you a number of checkpoints that could be evaluated and flight conditions adjusted (slip, tighten turns, hold flaps etc) as required to make the field.

If you did not have the necessary altitude to make all of the check points (Hi Key), you entered the pattern at a lower check point and went from there.

Is such a pattern taught in the civilian world??

I have not had a chance to build such a pattern yet with actual data from my RV-6 as I am just finishing Phase 1 - But I certainly will be doing it ASAP.
 
gereed75

"Is such a pattern taught in the civilian world??"

Yep, I was taught this when I got my private pilot's license here in the UK 5 years ago. Did it in the dark when I got my night qualification too. It's pretty much standard practice here.

Steve
RV-7 fuse
 
p.s. we didn't stop the engine though.... just brought it back to idle and and gave it a few seconds of increased revs a couple of times on the way down to stop the temps from dropping too much.
 
Polar and EFIS

the_other_dougreeves said:
Excellent! This makes a nice polar for your new RV-9G. Interestingly, your best L/D came at your minimum sink - L/D of 15.4 at 70mph and 400 fpm. 400 fpm and L/D of 15 means you have a lot of time to figure out what's wrong and pick landing spots if the engine quits at 9500 without warning.

<snip>
TODR
Click to expand...

Looking at the polar curve and the comments about it, I was just wondering if any EFIS recording system would offer some "Polar Calculation and Drawing" facility as a selectable option, i.e. press some "Start Recording Speed and Sink Rate" button when you're ready to reduce power to idle (or shutdown) and start experiencing with different speeds.
Maybe I'm dreaming, but there is so much computing power now in modern EFIS systems that I'm pretty sure it's just a question of writing the appropriate software routine.
Any EFIS manufacturer out there? :D
 
High Key

Gary,

This pattern consisted of arriving over your intended point of landing heading in the direction of intended landing at best glide airspeed (Hi Key) with about 2500' altitude AGL. From there you performed a constant AOB 360 degree turn to final. Flaps came down when the field was made.
Click to expand...

As for the USA civilian world, all I remember doing was a couple of ?simulated? engine outs, pick a field and see if you can make it. We never landed the airplane. I was out flying Young Eagles on Saturday and had a discussion with a retired General who flies an RV. He knew I had done the engine out and during the conversation we started talking about the military?s approach to training, regarding the high key and low key check points. First I had ever heard of that.

In my original post I mentioned that getting set up for the landing would be the hardest part of an actual engine out. This is where the military training would be most useful. The next time I get a chance to go and practice, :cool: determining the high and low key points for my plane is what I plan to work on. That?s going to be a while though as I head to Texas on Wednesday, with the plane, and should be there about a month.

Regards,
 
Emergency Landing Pattern

Yes, I was taught the 1000 ft emergency landing pattern when I took my transition training from Bob Lynch in Jeff City, MO. back in 2003. I showed it to my instructor back home and he started teaching it in the Cessna. It works great with all types of planes. It takes some practice to get the circle to land timed right, but once you have done it a few times, you will have confidence that you can always put it on the ground when you need to. (One less thing to stress out about when the **** hits the fan)
Good post, Scott.
Gene Larsen
Moody Blue
Travel Stories: www.GetBusyLivingNow.net
 
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