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Extended Glide...

smokyray

smokyray

Well Known Member
How far can your RV glide? We just returned from a humanitarian visit to the Bahamas, helping roof some hurricane damaged homes with another VAFer, WC. During our return we stopped to grab lunch at a small island along our route. Parked nearby was a Cherokee Six with a buckled cowling. Being a curious A&P I walked over to inspect. I found the LH cowling buckled and broken open and a quick glance inside showed why, 1 cyllinder had blown completely off the case. (I've seen this many times on Turbos) The windshield was completely covered with oil but the guy was able to glide to dry land from over 20 miles away at altitude, and a hard surface runway. Well done across the board and a happy ending.

This raises the question for you, how far can you glide? Have you practiced power off glides? In the F-16 we practiced glide approaches as a matter of currency, mandatory. It became almost mundane and when it really happened to me, the glide approach and landing wasn't too surprising(despite being on fire:eek: ). In my RVX I routinely set a hard altitude when coming home and reduce the power to idle at set distances to observe glide capabilities at different airspeeds. I have done this in my C/S HR2, my RV4 and many other RV's I fly on pre-buy inspections as part of my report.

Results? 87 KIAS in my RVX produces the best glide ratio producing a 10 mile glide to straight-in approach from 10 miles distant at 5K altitude, no wind. Your mileage may vary and you need to have a hip pocket number for when or if it happens to you. If you practice contingencies they aren't as much of a surprise when they happen for real. Or to quote General Patton: "the more you practice in peacetime, the less you bleed in war."

V/R
Smokey

 
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smokyray said:
...Results? 87 KIAS in my RVX produces the best glide ratio producing a 10 mile glide to straight-in approach from 10 miles distant, no wind. Your mileage may vary and you need to have a hip pocket number for when or if it happens to you. ...
Click to expand...

From what altitude?

Edit:I see your correcton... makes much more sense now.
 
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10.5:1 glide ratio? Seems pretty good. Are you pulling a C/S prop all the way back to get that? Best I can get with my 6A is about 9:1 with the prop not pulled back. I've pulled it back for simulated engine outs to landing, but not during glide ratio testing.
 
Fixed Pitch vs C/S

Hi Alex,

I have a FP Catto set at idle power to achieve the afforementioned numbers. My RV4 matched the X's numbers with a Catto at idle. One note about FP props is they don't windmill below 120 knots after engine failure, reducing drag slightly and thus extending glide.

I did extensive glide testing in my HR2 with IO-540 C4B5 and 2 blade Hartzell. Best I could ever get was 4.5:1 at idle. Several years ago, for experimentation I climbed my HR2 to 10K above an uncontrolled nearby former WW2 training base with three 5000' runways. I found after numerous different speed/power scenarios the best bet (if you have enough altitude) with engine failure (and you are not attempting an air-start) is to first slow down to 50 Knots (just above stall to stop the prop) and then establish a 90 KIAS glide. At 90 the prop won't windmill much and it increased the Rocket's glide considerably (nearly twice). I imagine this would hold true for any C/S RV. I also tried pulling the prop to coarse pitch after shutdown. Not enough oil pressure to increase pitch. The Hartzell goes flat pitch below 30 psi. The Cherokee 6 in the photo engine seized so the prop was frozen in place, yielding a 27NM glide from 13,500 feet.
One side note from all this glide testing was I noted that when best glide speed was established my cockpit air vents on both the HR2 and my RVX just begin producing airflow. Too slow and the air stops. Best glide AOA produces air every time. Interesting.

Smokey
 
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In my case

I did some engine out experimentation in my C/S -6. I got a descent rate of about 1100fpm at 80 KIAS with the engine dead (mixture ICO) and the prop at full increase. I figure a glide of about 8:1 in this configuration.

I know that pulling the prop back to coarse pitch, WOT helps about 20%. I do not use this in practicing as I figure it is best to practice worst case. You may not be able to adjust the prop in an actual situation.

It will improve even more with a stopped prop. As noted, you need to get close to stall to stop it. With a stopped prop, I suspect you would see 10:1 and 700 fpm or so. It might come in handy in a high altitude situation when you have time to take advantage of the extra glide.

Again, I do my practicing at 1100 fpm, 8:1 and use the military High Key- Low Key ELP pattern. I try for a 1500' AGL High Key that makes a very comfortable pattern at 20 degrees AOB. It takes about 600'-700' per 180 degrees of turn. Ideally that get's you to short final with 200-300' that can easily be killed off with flaps when you know you have made the field.

Hopefully in an actual, when appropriate, I can use the prop speed improvements to get a bit better glide.


Practice, practice , Practice. You'll react like you train when the real thing happens. Not sure how you'll react if you have'nt practiced!!
 
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best practice....etc.

hey guys, can you provide a little 'Glide 101' for us newbs who haven't the benefit of much 'real' training?
I looked up the 'High-Key....' approach,
thanks to your link, but the definition leaves a few questions.

For example, if you enter the hi-key side, but find for whatever reason your rate of descent, or entry altitude less than optimal, how can you correct it and still get on the right arc-to-final that is essential to a happy outcome?

I can see some argument for the overhead break type tear-drop approach....although perhaps requiring more skill, and constant correction of glide angle, airspeed and radius.

....we're out here listening! :)
 
Thanks for asking and wanting to learn.

Try this https://www.cnatra.navy.mil/pubs/folder5/T34C/P-330_CH9.pdf

It might take some finagling to get your browser to go there, but it is worth it.

See section 8. The RV's and the T-34 are somewhat close in flight characteristics. Instead of 2500' AGL, use 1500'. Instead of 100 KIAS, use 80 KIAS and I use more AOB - 20 +/- instead of 10 - 15 degrees.

The rest of the info applies. It gives you a planned set of reference points from which to judge your progress to the field. Fly the check points, you'll make it!! No guess work involved!!

The important thing when practicing is to be able to simulate the same glide characteristics that your plane will have in the event of an actual engine failure. For me, that is engine at idle, and just about 10 degrees of flap. That gives me the same descent rate as engine out and clean. (pull the red handle and set up a glide to see what it is for your airplane (of course over a field in case you do not get a re-start, YMMV, disclaimer disclaimer)).

Read and practice. If you can't make it to High Key, intercept the pattern at some point below High Key and then pick up the check points.

While your at it, check the section on landing pattern work - again, all by the numbers!!
 
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AOA

Could an AOA indicator be used to maintain best glide along with airspeed? It seems like it could with some experimentation.
 
Yep, AOA is a better judge of the performance. Maybe for a jet with rock like glide characteristics it might be essential, but within the performance envelop of the typical RV, I would say airspeed gets you close enough.

Probably easier for the average schmoe to scan and nail airspeed than chase AOA. When I practice, it is tough enough holding airspeed +/- 5 knots, not sure what that would look like in AOA.
 
All keyed up...

Perry,

Thanks again for your query. SFO patterns or "simulated flameout" are practiced regularly by single engine Jet (or prop) guys, usually over an airfield of some sort. The F-16 SFO overhead pattern resembles a descending spiral 360 degree turn to final normally began overhead the "numbers" on runway heading at "High Key". High, Low and Base "Key" are pattern positions with altitude references for completing a safe approach. Normally High Key is at 8-10K' AGL. Low Key 3-5K and Base Key at 1-2K. Straight-in SFO's normally start at 7000' AGL at 10 DME.

In the F16 the numbers are based on 6 units of AOA regardless of weight or configuration. That works out to be around 210 Knots for best glide. In a pinch though the HUD flight path marker can be used to determine whether you will make the runway or not. You simply place the flight path marker on the "numbers' of the airport and if the airspeed increases, "Bob's your Uncle". If not, C'est la vie...

In RV's the SFO can be flown as low as 1000 AGL over the runway or 3 mile final at 1500'. Yes, as mentioned above AOA can be used and works extremely well. Practice makes perfect. Trust me when the feces hit the proverbial terra firma, you'll be glad you did.

Smokey

http://www.youtube.com/watch?v=vithNm877tU
 
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The Garmin X96 units have a glide ratio function that can be selected so that it always shows up on the flight parameters page. Once done, just go to that page and adjust your pitch until your glide ratio is maximized. Very handy, and you can experiment with different wind conditions to see how the best airspeed for maximizing your glide changes. See
http://www.vansairforce.com/community/showthread.php?t=65229&highlight=glide+ratio
for further discussion.

erich
 
AOA vs. IAS and gliding in a wind

gereed75 said:
Yep, AOA is a better judge of the performance. Maybe for a jet with rock like glide characteristics it might be essential, but within the performance envelop of the typical RV, I would say airspeed gets you close enough.

Probably easier for the average schmoe to scan and nail airspeed than chase AOA. When I practice, it is tough enough holding airspeed +/- 5 knots, not sure what that would look like in AOA.
Click to expand...

Not all AOA's are equal. The LRI has a very good moving needle and is easily as precise as IAS. You can see mine on my website. If you can find the right indication on the AOA then you don't have to think about weight. If you are heavy vs light, there can be 5 mph or more difference. Try it and see for yourself. The observed behavior of the vents is interesting and I would guess is an AOA rather than IAS linked event, but I can't know for sure.

Now a word of caution: in a zero wind, the best glide is at the bottom of the curve that forms where parasite and induced drag cross. (Note that the kind and setting of the prop changes the curves.) BUT, the usual "thumb" rules often taught by well-meaning instructors about what to do with head or tail winds are, IMHO just plain wrong and often introduce too much correction. They do this, perhaps, because they don't factor in the curve. Also on my website is this spreadsheet:
http://home.cogeco.ca/~n17hh/Models/GlideInWind.xls which will demonstrate my point and, if you download and save a copy, will allow you to experiment with it, too. If there is less than 5% wind, ignore it, but if there is a significant wind, as you will see, an adjustment would be a very good idea at a very bad time.

A GPS that gives groundspeed and your knowledge of your ASI's calibration can become important in evaluating this problem in the required instant that you may have as things get quiet. An EFIS that gives TAS accurately can be important, too, since then you know TAS vs. GS = HW or TW. Your best glide speed has to be determined by AOA or IAS, but the adjustment for wind requires that you know GS and TAS. Yes, I can hear you saying "why does he make it so complicated?". Well, it just is. Otherwise, use a sticky note and fly the darn thing.
 
YES!

erich weaver said:
The Garmin X96 units have a glide ratio function that can be selected so that it always shows up on the flight parameters page. Once done, just go to that page and adjust your pitch until your glide ratio is maximized. Very handy, and you can experiment with different wind conditions to see how the best airspeed for maximizing your glide changes. See
http://www.vansairforce.com/community/showthread.php?t=65229&highlight=glide+ratio
for further discussion.

erich
Click to expand...

Absolutely right!
 
As smokey says, you can make the field from 1000' AGL High Key, but that gets pretty tough.

You have to wrap up the turn and hold flaps to do it. I like 1200' minimum for a comfortable pattern.

Do the math, for 80 knots, 15 degrees AOB is a Standard rate turn, so 20 degrees AOB is more than a standard rate turn. So the 180 degree turn (High Key to Low Key) will take about 40 secs. At 1100 fpm descent, thats about 730'. So from 1500' your now down to 750' AGL. 40 more seconds to line up with the runway and your rolling final with 100'AGL or less.

That's why I use 20 - 25 AOB to get 200+ feet on final with some altitude to play with. Starting at 1200 ft and 25 AOB might get you to final with little time for flaps, except maybe in the flair.

Obviously you want flaps down to get the lowest stall speed (and touch down speed as possible).

Remember, length of field permitting, your shooting for a touchdown spot 1/3 of the way down the runway. That gives you a bit more gravy for a low entry.

Again, practice with different entry altitudes and AOB's etc etc. It will get to be very routine after a few.

Thanks Heaven, as usual, very good info. I am glad to hear about the LRI, as that is what I will be installing during my next major down time.

Our rule of thumb for the ELP pattern was to use a steeper AOB as the wind went to the tail and a less steep AOB as you turned into the headwind. How does that square with the theoretical??
 
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RV-4 Glide

We have an RV-4 with a fixed-pitch Catto. Measured glide ratio is 13.2:1. Maximum range glide occurs at 80 MPH CAS at 1500 lbs gross weight. Maximum endurance glide occurs at 70 MPH CAS at the same gross weight. Speeds decrease as weight decreases. Overall glide performance improves with the propeller stopped. The maximum performance numbers don't provide much energy (maneuverability) reserve, so we can achieve a base-line 10:1 ratio using 100 MPH IAS (a nice round number coincident with the top of the white arc on the airspeed indicator). Winds aloft can make a big difference in the amount of ground you can cover. The emergency checklist has a quick reference table with 10:1 glide ratio numbers that assist with computing time and distance to high-key (or, if things aren't going so well, minimum controlled bail-out altitude).

For a flame-out pattern, I fly high key at 1500-1700 AGL (using the low number if 100-105 MPH or high number at 80 MPH), to arrive at low-key at 800-1000 AGL. High key is located right above the TDZ flying in the direction of intended landing, the same as a 360 overhead approach. At low key, I slow to 80 if I haven't already done so. I fly a 180 degree descending turn, adjusting the perch position (where you start the turn) and bank angle throughout the turn to arrive on final at 300 feet AGL 3000' from the TDZ. Flaps are held "in reserve" and liberal use of slips helps take some money out of the bank if you have some excess energy. These are the same techniques you use flying a turn around a point, but it's even easier if you visualize the point at which you want to roll-out by picking a spot on the ground 3000 feet from the intended touchdown point. One thing I've found helpful is that my "standard" pattern is flown almost identically to my "emergency" pattern--i.e, power to idle, full flaps and roll off the perch at 80 MPH IAS. The only thing I do different in an emergency, is hold off slightly on the application of flaps to put a little money in the bank that I take out by either slipping or adjusting the ground track slightly. I practice a full flame-out pattern to touchdown or low-approach at least a couple of times per month to stay proficient.

Each RV is different, with one of the most important variables being the type of prop installed. The RV-4 with a light weight composite prop optimized for cruise is a veritable motor glider compared to a heavy RV-8 with a constant speed prop, so some testing is required to determine actual glide performance and the numbers required build a flame-out pattern.

Fly safe,

Vac
 
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I have done a bunch of these over the years in the military and did a bunch in my 6 last fall. Gary made the point about shooting for 1/3 of the way down the runway. You don't want to touchdown on the numbers unless the runway is so short you have no other option. I use the 270 pattern as a matter of choice however both the military and others will use a 360 degree pattern depending on the aircraft. I prefer the 270 pattern because I feel it gives me a better look at the airport and airport traffic inbound. It is however a personal choice. I have found that 1500 feet AGL works great. I attempt to cross the runway at 1500 feet AGL with the aircraft at 80 knots and half flaps. I use half at that point because it gives me the option to bring them up if I were to come up short. If I am going to land long they go to full and the aircraft can be slipped. Varying the bank angle in the turn can also adjust both short and long. That is what makes the continuous bank circle type pattern nice. There are lots of ways to adjust the touchdown point. As mentioned once you figure out a pattern that works and get the altitudes fixed in your mind you can intercept the pattern at any point.

George
 
smokyray said:
I did extensive glide testing in my HR2 with IO-540 C4B5 and 2 blade Hartzell. Best I could ever get was 4.5:1 at idle. Several years ago, for experimentation I climbed my HR2 to 10K above an uncontrolled nearby former WW2 training base with three 5000' runways. I found after numerous different speed/power scenarios the best bet (if you have enough altitude) with engine failure (and you are not attempting an air-start) is to first slow down to 50 Knots (just above stall to stop the prop) and then establish a 90 KIAS glide. At 90 the prop won't windmill much and it increased the Rocket's glide considerably (nearly twice). I imagine this would hold true for any C/S RV.
Click to expand...

The results with my three-bladed MT aerobatic CS prop differed considerably from Smoky's experience. With my prop it is extremely difficult to get the engine to stop windmilling. It takes over two minutes on the edge of the stall with full flaps before the engine will stop turning. The prop starts turning again somewhere between 90 and 95 kt. The glide ratio during that long two minutes with full flap to stop the prop is so poor that it there is no point to trying it unless the engine failure occurs above 15,000 ft. Otherwise you would have lost so much extra altitude while stopping the prop that there is no way to make up it.

With all three engine levers full aft (throttle closed, prop full aft and mixture ICO), and the prop windmilling, best glide ratio on my aircraft is about 8.75:1 about 104 kt at 1600 lb weight.

Test results here.
 
Hey Smokey

I never knew that a Zoomie would go to that length just to get into Cubi - straight from RWY 7 to the club for a Cubi Dog and a pitcher of Cubi Specials.

You rascal!!
 
Good discussion! I've practiced a few SFOs in my RV as well (PPELs in Navy parlance...Practice Precautionary Emergency Landings...everyone love acronyms, eh! ;)). Sounds like our numbers are relatively consistent.

With my clipped wings and heavier airplane, and the field at 5K MSL (probably 7K DA during practice sessions), and I found 1800' AGL to be a comfortable hi key with the prop in, and 1500' do-able with the prop pulled full out. I played with a high key down to 1200' agl, and that was marginal at best (that day, those conditions). So I've settled on 1800' (hi DA) and 1500' (SL) as hi key targets. I'd take more if I can get it, as you can adjust the pattern (and/or slip) to hit the touchdown zone if needed.

I need to re-do this with my new prop (traded the D-twist paddle for a BA) to see if there is a notable difference. I also need to play with some glide ratio testing.

Good posts guys! Valuable info and good training...useful tools so you can plan to hit a hi key from any direction to the airport, or need to call the audible as you close on the airport, head for the nearest landing surface, and slip it in to the most suitable runway (or piece of concrete).

Cheers,
Bob
 
Starter motor?

Has anyone measured the change in glide with the engine at ICO, with and without using the starter motor? I'm assuming WOT would be best.

Just wondering..
 
In our RV-10

We can glide 2 nm from 1000' agl with throttle and prop knobs all the way back at 80 kias and full gross wt. I have a label on top bezel of my grt with "Glide 1.5 nm/1000' agl". As were flying cross country my wife and I will judge if we could make it to a particular airport taking winds into acct, then calculate it using the nrst func on the 430w or 496. Something we learned...You cannot use smoke as wind dir indicator above 1000' agl and wind direction/speed can change 90 deg or more within a few miles. Gotta love glass. Never knew when in flight training and was told to just use ground references for wind dir. If up high this grt display could mean the difference in making or not making a particular landing spot. It is our fifth flight as a family together. So far one full stall and some slow flight with them on board. We will be doing some sim eng outs later. Lots for us to learn. My wife is learning all the avionics within reach of her which really helps out.
 
Help?

I still can't find the glide ratio information on my Garmin 496.

Is it in "Setup". If not, then where?

Thanks,
 
pierre smith said:
I still can't find the glide ratio information on my Garmin 496.

Is it in "Setup". If not, then where?

Thanks,
Click to expand...


With the unit on, push the " page" button until you reach what Garmin calls the " position data page". It will have the compass heading tape at the top and various data types, like speed, altitude, flight time, etc. displayed in multiple boxes on the screen. Press "menu", then highlight "change data fields" and press "enter". Using the rocker button, move the field highlight to the data field you are willing to get rid of and replace, and hit "enter". Press up or down on the rocker button to scroll through the available data types and highlight the one you want (glide ratio). Press "enter". Press quit to exit.



Good luck
Erich
 
Great Info!

erich weaver said:
With the unit on, push the " page" button until you reach what Garmin calls the " position data page". It will have the compass heading tape at the top and various data types, like speed, altitude, flight time, etc. displayed in multiple boxes on the screen. Press "menu", then highlight "change data fields" and press "enter". Using the rocker button, move the field highlight to the data field you are willing to get rid of and replace, and hit "enter". Press up or down on the rocker button to scroll through the available data types and highlight the one you want (glide ratio). Press "enter". Press quit to exit.



Good luck
Erich
Click to expand...

I did mine today as you said! Works great, I went up and played with it some just to familiarize myself with it. This is a great feature that I will definitely use and learn from. I wasn't able to get any useable info as the winds were 25kts or so and very bumpy. Thank you for posting this information for all of us that don't read our manuals. Allan:D
 
Kevin Horton said:
The results with my three-bladed MT aerobatic CS prop ... The prop starts turning again somewhere between 90 and 95 kt.
Click to expand...
Kevin, do you remember whether the prop was in coarse or fine pitch at the time? I'm surprised the prop would start turning so easily, although having three instead of two blades to catch air and start it may explain it. Also, I guess the aerobatic prop goes to coarse pitch if pressure is lost... That would make it easier to start windmilling than a fine pitch prop.
 
Snowflake said:
Kevin, do you remember whether the prop was in coarse or fine pitch at the time? I'm surprised the prop would start turning so easily, although having three instead of two blades to catch air and start it may explain it. Also, I guess the aerobatic prop goes to coarse pitch if pressure is lost... That would make it easier to start windmilling than a fine pitch prop.
Click to expand...
I've got an aerobatic prop, which goes to full coarse pitch once there is no oil pressure. So, with engine stopped, the prop is coarse.
 
496 glide

With the 496 glide function tip, I have a reason to do some gliding with my -7.

Thanks for the tip.
 
erich weaver said:
With the unit on, push the " page" button until you reach what Garmin calls the " position data page". It will have the compass heading tape at the top and various data types, like speed, altitude, flight time, etc. displayed in multiple boxes on the screen. Press "menu", then highlight "change data fields" and press "enter". Using the rocker button, move the field highlight to the data field you are willing to get rid of and replace, and hit "enter". Press up or down on the rocker button to scroll through the available data types and highlight the one you want (glide ratio). Press "enter". Press quit to exit.

Good luck
Erich
Click to expand...

THANKS for the tip. I know what I will be doing on my next flight. :cool:
 
Good to see interest in Garmin glide function

I based a major part of my "research" on this feature. It's all in the presentation I have at Airventure in 2010 and the link is on my website.

Just be aware that the glide ratio it reports is affected by wind.
 
More Info!!!!!!

I for one do not understand why Vans fails to publish more performance information on all their models of aircraft. I wish they would make public their test results as to best glide speed, angle etc. as well as all the v numbers. If they did it would greatly simplify all of this self testing and trying to gather our own information. If nothing else it would be a starting point and a way of comparing your aircraft to theirs. In my case I would like all the information and test results for the 9-A. I have searched the net and found very little of this information and what I have found I am not sure how reliable it is. Should you know where to find this I would be grateful for a link in that direction. Regards all, Allan :D
 
PerfTech said:
I for one do not understand why Vans fails to publish more performance information on all their models of aircraft. I wish they would make public their test results as to best glide speed, angle etc. as well as all the v numbers. If they did it would greatly simplify all of this self testing and trying to gather our own information. If nothing else it would be a starting point and a way of comparing your aircraft to theirs. In my case I would like all the information and test results for the 9-A. I have searched the net and found very little of this information and what I have found I am not sure how reliable it is. Should you know where to find this I would be grateful for a link in that direction. Regards all, Allan :D
Click to expand...
The problem with Van publishing V speeds is that the climb V speeds are dependent on the engine and prop. The descent V speeds are dependent on the prop.

If you specified a particular engine and prop, the values in CAS would be pretty accurate for all aircraft of that model. But, to be useful, you need values in IAS, and the airspeed system error depends on the ASI instrument error and the static system position error, both of which will vary from aircraft to aircraft.

So, any V speed data that Van published could not be assured to be valid for any given aircraft.
 
SPECS!!!!!!

Kevin Horton said:
The problem with Van publishing V speeds is that the climb V speeds are dependent on the engine and prop. The descent V speeds are dependent on the prop.

If you specified a particular engine and prop, the values in CAS would be pretty accurate for all aircraft of that model. But, to be useful, you need values in IAS, and the airspeed system error depends on the ASI instrument error and the static system position error, both of which will vary from aircraft to aircraft.

So, any V speed data that Van published could not be assured to be valid for any given aircraft.
Click to expand...

I know it will change, mostly with propeller choice, but the majority of say 9-A models have 0-320/160 fixed pitch and it would be nice to know what Vans test model did if for no other reason than something to compare or shoot for. I just find it odd that all these numbers are for the most part unaddressed. If they were to publish their test results it would be considered by most to be the gospel. Thanks, Allan:)
 
PerfTech said:
I know it will change, mostly with propeller choice, but the majority of say 9-A models have 0-320/160 fixed pitch and it would be nice to know what Vans test model did ...
Click to expand...
Van's test models don't have that configuration (unless they flew one early on that was kept under wraps)....
But the data with the two props that they have used would be nice.
One is on the CAFE article... An update with the 2 blade would be nice.
 
We practice these every month and figure on 8 to 1 at 85 knots IAS on the 6A. Always good to know and be current just in case...
 
what are the right numbers????

I too would like some numbers for a -9a, as a baseline at least.

For those of us that aren't test pilots ( Kevin et al) our POH is a bunch of guesses and suppositions.
For instance, my aircraft's builder ( and Phase I pilot ) provided an excellent graph plotted to show rate of descent at various airspeeds..... it's a perfect parabola, except for one point that's way off. Do I use this point?
Is it a mistake caused by data collection error or less than ideal test conditions? or is it a hard fact, due to an aerodynamic condition at that particular loading, AoA, speed etc.

Ross, no fair practicing your glide, out where the ground is clearly marked in a flat, one-mile square grid!!! :) what's a guy to do in the mountains????
 
flyboy1963 said:
I too would like some numbers for a -9a, as a baseline at least.
Click to expand...
We used the CAFE report numbers as a baseline to start with and then either verified or updated the numbers as necessary.

Generally, the numbers were within a couple of what we measured. :)

The glide numbers were a little different likely do to the difference between the three blade prop tested and our 2 blade.

One think that we learned was the getting consistent test numbers in varying conditions can be difficult:eek:
 
Glide

MauiLvrs said:
We used the CAFE report numbers as a baseline to start with and then either verified or updated the numbers as necessary.

Generally, the numbers were within a couple of what we measured. :)

The glide numbers were a little different likely do to the difference between the three blade prop tested and our 2 blade.

One think that we learned was the getting consistent test numbers in varying conditions can be difficult:eek:
Click to expand...

The Cafe report was really great and I use it also. You said that the glide numbers were different with the two blade prop. Can you tell me the two blade cs numbers? Thanks, Allan
 
Glide and gliders

As a long time glider (sailplane) person, I recommend a few flights in a glider for any pilot. Your stick and rudder skills will improve dramatically and you'll have the opportunity to verify airplanes can fly without a fan. Energy management is the key and that's all one has in a sailplane.

No the glide ratios are not comparable but "don't stop flying when the fan stops" will have new validation.

Dan Jopling
 
flyboy1963 said:
I too would like some numbers for a -9a, as a baseline at least.

For those of us that aren't test pilots ( Kevin et al) our POH is a bunch of guesses and suppositions.
For instance, my aircraft's builder ( and Phase I pilot ) provided an excellent graph plotted to show rate of descent at various airspeeds..... it's a perfect parabola, except for one point that's way off. Do I use this point?
Is it a mistake caused by data collection error or less than ideal test conditions? or is it a hard fact, due to an aerodynamic condition at that particular loading, AoA, speed etc.
Click to expand...

Glide performance should vary smoothly as the speed varies. There will be some noise in the data, and there are many reasons why any given point could have a large error. So, if all the points but one make a reasonably smooth curve, I'd suspect that one point was bad, and throw it out.

The one exception is if the bad point is an end point on the curve. Maybe something major happens that changes the shape of the curve, and this strange end point is simply the first sign of it. In that case I'd do another flight to get more data in a range of speeds straddling the strange data point.
 
Some Testing!!

...I went back out to do some testing last weekend as the weather was dead calm and clear as a bell. I have my Garmin set to glide ratio (love this feature) and wanted to try to get some accurate numbers. I used all the speed, weight etc. like the Cafe tests and corrected for any minor variations. I did the tests several times in different directions and found that my glide numbers were actually a little better than the Cafe tests at 12.2 to 1. It appears that my Whirlwind two blade RV-200 prop is the difference. The two blades verses three blades is less drag and my stops are set where course pitch is extremely aggressive (closer to feather) than the MT that Cafe used in there tests. I also tried to gather some numbers with prop stopped, and that really made a huge difference. I didn't get to run as many tries as I would like as it was getting late but the ones I did averaged together were 12.9 to 1. Needless to say I was impressed. This little airplane (RV-9) just keeps amazing me time after time the longer I fly it. Regards all, Allan :D
 
RV9 Glide

Impressive numbers (12.9-1). That is an efficient wing. What engine do you have? You can glide much farther than my 7.

Thanks for posting Allan.
 
NickAir said:
Impressive numbers (12.9-1). That is an efficient wing. What engine do you have? You can glide much farther than my 7.

Thanks for posting Allan.
Click to expand...

My engine is an 0-320/160hp from Aero Sport Power, the prop is a slightly modified version of the RV-200 Whirlwind C/S. Allan:D
 
Allan

Any glide comparison data between "Prop full Increase - max RPM" and "prop full decrease - min RPM" settings??

This might provide some relative data for us guys with RV-200's who don't have the GPS glideslope function.

I know my glide is much better at min RPM, but it would be nice to know how much better. I know my 6 won't get the same numbers as your 9, but the % difference would probably be comparable.

Thanks
 
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