Best Glide Vs Best Sink... RV7 numbers ?

[BillSchlatterer]

Just curious what folks are using for Best Glide and Best Sink rates in the RV7A with 360/CS or similar 7 or 8? What are you putting in your POH if you have one?

I'm using 85-90 MPH for best sink and 100-105 MPH for Best Glide. Anybody done any real measurements ??


Thanks Bill S

 

[mgomez]

From Roberta Hegy?s POH

...see the glide chart.

http://www.vansairforce.net/POH/n2447Apoh.doc

 

[BillL]

Just curious what folks are using for Best Glide and Best Sink rates in the RV7A with 360/CS or similar 7 or 8? What are you putting in your POH if you have one?

I'm using 85-90 MPH for best sink and 100-105 MPH for Best Glide. Anybody done any real measurements ??


Thanks Bill S

Bill, not sure about best sink, but the best glide (tangent to curve) with my RV7, engine at idle (4 test points) was 103KTAS (87KIAS) for my plane at about -940 FPM. With the engine windmilling (mix pulled) I only got two points the one closest was 105 KTAS , -1000FPM as measured resulting in a 9.7 glide ratio. Tanks were near full, 160lb in cabin, empty GW is 1140lb. The test was between 9-8000 ft. While speed (103KTAS) and descent rate (-940) are taken from the graph/data points, the other info is from memory. If it is important, it can be verified. Prop pulled out fully. I have the Hartzell composite and at fine pitch, glide is much different (8% less).

Important note: This if for reference and will not likely represent any other aircraft model or serial number.

 

[alpinelakespilot2000]

I'm using 85-90 MPH for best sink and 100-105 MPH for Best Glide. Anybody done any real measurements ??

Anyone who has built their plane should have real measurements derived from phase 1 testing, and every plane will be a bit different due to static/pitot/asi instrument/weight particulars. Bottom line, you really need to do this testing for your plane and, in any case, is probably beneficial anyway for a non-builder to help them get to know their plane better. It’s easy to do and good for polishing piloting skills as well.

Have fun.

 

[SuperCubDriver]

I did some testing with my RV-7 and came up with a best glide speed of 80 KIAS, 1,6 NM still air distance per 1000ft, gliding range almost 1:10. Most testing was done with close to max weight and between 5000 and 10000 ft with power at idle (windmilling) and prop at low pitch. Numbers are rounded as they are dependent on weight and so a little variable.

 

[uk_figs]

Interesting discussion

In my case (RV-7) best glide is around 110 mph, fixed pitch Catto 3 blade with heavy sabre spacer and landoll ring approximating a CS weight up front. Rate of descent around 500 ft per min (approximated prop windmilling at idle rpm).

I actually built a glide range chart (no wind) with altitude and terrain height as one of my check lists to quickly see if I could make a runway when punching "nearest" on the 796 in case of an engine failure, now superseded by the glide range ring in Foreflight.
YMMV
Figs

 

[RV7A Flyer]

Some recent retesting to more accurately find Vbg found ~95 KIAS, pilot + passenger, no baggage, about 3/4 tanks.

Seems in line with most others, but then I see some that are WAAAY lower, like 75 or 80 KIAS.

How can there be such wide variation in the same airframe? They're all RV7s, probably about the same weight give or take a little...75 knots all the way up to 103 knots? That's nearly 40% increase from 75 to 103...doesn't make sense to me.

 

[BillL]

Some recent retesting to more accurately find Vbg found ~95 KIAS, pilot + passenger, no baggage, about 3/4 tanks.

Seems in line with most others, but then I see some that are WAAAY lower, like 75 or 80 KIAS.

How can there be such wide variation in the same airframe? They're all RV7s, probably about the same weight give or take a little...75 knots all the way up to 103 knots? That's nearly 40% increase from 75 to 103...doesn't make sense to me.

I think we are all reporting in different conditions, altitude, temperatures, props, and weight. I reported 103 KTAS, at 9000 ft. Precisely, that is 87 KIAS for barometer and temp of that day. I am not a test pilot so did not know how to report in "standard" conditions. A recent Kitplanes article by Nigel, recommended testing a several altitudes. I only tested in one region. If you have a recommendation of a correction procedure for this testing, and a standard condition, please post, I'll do the calculations and report accordingly.

 

[RV7A Flyer]

I think we are all reporting in different conditions, altitude, temperatures, props, and weight. I reported 103 KTAS, at 9000 ft. Precisely, that is 87 KIAS for barometer and temp of that day. I am not a test pilot so did not know how to report in "standard" conditions. A recent Kitplanes article by Nigel, recommended testing a several altitudes. I only tested in one region. If you have a recommendation of a correction procedure for this testing, and a standard condition, please post, I'll do the calculations and report accordingly.

Good point about the different atmospheric conditions/altitude. I don't have a procedure or analysis for computing Vbg at a specific altitude/density altitude, but someone might (given, say Vbg at another specific point). I did miss that you were reporting TAS, whereas I think most people understand all V-speeds other than Vne to be in IAS.

Still...quite a range of values for similar aircraft.

 

[Capt]

Good point about the different atmospheric conditions/altitude. I don't have a procedure or analysis for computing Vbg at a specific altitude/density altitude, but someone might (given, say Vbg at another specific point). I did miss that you were reporting TAS, whereas I think most people understand all V-speeds other than Vne to be in IAS.

Still...quite a range of values for similar aircraft.

It's always interesting to read what pilots get out of their machines, much can be learnt from these pages I Like the last bit, VNE to be in IAS, I still hear pilots say VNE is what's on the dial at high Altitudes, now that's a worry!

 

[paul330]

As mentioned, you need to test to find your own numbers, Also bear in mind that whatever you come up with, these are theoretical numbers. It is generally preferable to fly slightly on the fast side for several reasons:

- it makes little difference to the glide angle
- helps with any headwind
- further from the stall especially as some heavy maneuvering might be required
- leaves a bit more energy for that final glide to touchdown if you are a bit short

 

[ColoCardinal]

Best glide

As mentioned, you need to test to find your own numbers, Also bear in mind that whatever you come up with, these are theoretical numbers. It is generally preferable to fly slightly on the fast side for several reasons:

- it makes little difference to the glide angle
- helps with any headwind
- further from the stall especially as some heavy maneuvering might be required
- leaves a bit more energy for that final glide to touchdown if you are a bit short

I would add that it gives you a little margin for the natural tendancy pull up as you speed towards earth without power.
Been there!

 

[calpilot]

Best glide is like engine out VY , (feet per MILE!) (92 KIAS in my aircraft, windmilling, prop coarse pitch).
Minimum sink airspeed is like engine out VX (Feet per Minute) is (77 KIAS - same configuration as above)

So, 77 knots will give you most time in the air, and 93 knots will give you most distance.

DAR Gary

 

[KiloFoxtrot]

Best glide is like engine out VY , (feet per MILE!) (92 KIAS in my aircraft, windmilling, prop coarse pitch).
Minimum sink airspeed is like engine out VX (Feet per Minute) is (77 KIAS - same configuration as above)

So, 77 knots will give you most time in the air, and 93 knots will give you most distance.

DAR Gary

Very good explanation.

 

[Taltruda]

Best glide is like engine out VY , (feet per MILE!) (92 KIAS in my aircraft, windmilling, prop coarse pitch).
Minimum sink airspeed is like engine out VX (Feet per Minute) is (77 KIAS - same configuration as above)

So, 77 knots will give you most time in the air, and 93 knots will give you most distance.

DAR Gary

I think you got Vx and Vy backwards.. Vy is RATE (Altitude per unit time) while Vx is ANGLE (Altitude per unit horizontal distance)

 

[Bevan]

My opinion is it’s too hard to say with enough certainty to put it in your POH. These are not type certificated airplanes. Meaning there’s lots of variability. For example, you didn’t say what prop, engine, static port location etc you have installed. In exchange for the privilege of building your own comes the responsibility to test and make your POH based on actual testing. If you do, your POH and flying skills/knowledge will be better for it.

Bevan

 

[MikeyDale]

Best Glide in my 7 is 100 mph mixture pulled and prop coarse.

 

[calpilot]

You are correct, darn dyslexia!
Thanks for catching that,
Gary

I think you got Vx and Vy backwards.. Vy is RATE (Altitude per unit time) while Vx is ANGLE (Altitude per unit horizontal distance)

 

[calpilot]

For those with Garmin G3X, there is a new software update which will paint the glide area capability, based on the best glide entered by the operator, and terrain around the aircraft terrain. (Wind can still be a big variable).
DAR Gary

 

[Mel]

You are correct, darn dyslexia!
Thanks for catching that,
Gary

You might consider joining "DAM" (Mothers Against Dyslexia).

 

[Ralph Inkster]

Just curious what folks are using for Best Glide and Best Sink rates in the RV7A with 360/CS or similar 7 or 8? What are you putting in your POH if you have one?

I'm using 85-90 MPH for best sink and 100-105 MPH for Best Glide. Anybody done any real measurements ??


Thanks Bill S

An accurate Best Glide speed may be your best & ONLY friend one day. So wouldn't it in your best interest to determine what that number is - for your aircraft with your airframe/engine/prop model/C0fG/etc... combination?
While you're at it, get the EAA Flight Test Manual & build your own accurate for your airframe POH. Web POHs are for the most part good templates - but you should edit the content to your specific test resulted numbers.

Just a thought...

 

[Mel]

Distance Vs Altitude Loss.....

The question between distance or altitude depends completely on the situation. If you are quite a distance from an airport, then obviously you want distance. OTOH, if you are relatively close to a suitable airport, then you might opt for minimum altitude loss so that you might have more time to troubleshoot the power-loss problem. I have a VHS tape from many years back that does a very good job of demonstrating all scenarios. The tape was from ABC's "Wide World of Flying". I think it was Barry Schiff flying a C-182. He demonstrates both glide distance and altitude loss with engine at idle (with both fine and coarse prop positions) and with prop stopped.
I'll see if I can find it and give more information.
I had to take Ann to the emergency room yesterday, so I'm a little busy right now.
As said before, you need to find the best numbers for YOUR airplane.

 

[rv8ch]

...
I had to take Ann to the emergency room yesterday, so I'm a little busy right now.
...

Mel, I hope she has a speedy and full recovery! Not the place you want to be right now with the holidays and other stuff going on. Take care!

 

[wcalvert]

Glide distance based on an external reference

During phase I did some engine out glide numbers in the 5k down to 3K' test range (actual stopped prop, 3 blade Catto, -7) at different headings towards the airport to account for wind. GPS data was recorded and pulled from the Dynon HDX for analysis. Depending on weight, the best range glide speed was in a range of 75 to 80 kias.

The best info from these tests came from the concept of judging glide distance based on an external reference on the aircraft.

A talented Cub driver worked with me on the idea (he uses it in his Cubs) and we found that at my seated height, everything that was under my left wingtip was reachable in a power off glide. We did the calculations based on the computed data from my tests and converted it into a glide angle.

I've done more tests with power at idle, reduced power etc and have been pleased with the results.

Being able to look out the window when the noise stops and have a quick idea of how far you can make is nice. I find myself doing it all the time during cruise while playing the "what if" game. Keep in mind that this data applies to an aircraft already at best glide speed, so if your cruise is well above that number (as it normally is), that extra airspeed is all gravy.

Fly well

Cheers

 

[Philz7A]

What about prop in low pitch? If your engine quits and is windmilling, you will not have enough oil pressure to go to course pitch. You will be stuck in low pitch/high RPM correct? Resulting in a much lower glide ratio with a lower best glide speed compared to prop in high pitch, which I see many people say they are using.

 

[wirejock]

What about prop in low pitch? If your engine quits and is windmilling, you will not have enough oil pressure to go to course pitch. You will be stuck in low pitch/high RPM correct? Resulting in a much lower glide ratio with a lower best glide speed compared to prop in high pitch, which I see many people say they are using.

Yep. It's good to fly some tests. CS comes down pretty quick on low pitch.

 

[Taltruda]

What about prop in low pitch? If your engine quits and is windmilling, you will not have enough oil pressure to go to course pitch. You will be stuck in low pitch/high RPM correct? Resulting in a much lower glide ratio with a lower best glide speed compared to prop in high pitch, which I see many people say they are using.

There are a couple of scenarios where you cannot pull the prop to high pitch/low rpm to extend the glide. Loss of oil or oil pressure (hole in case, blown hose, oil pump failure), and governor failure to think of two. All the more reason to check and adjust the prop low pitch stops.. 2,550 to 2,650 static are acceptable, with the lower number (higher static pitch stops angle) giving better glide.

 

[Philz7A]

There are a couple of scenarios where you cannot pull the prop to high pitch/low rpm to extend the glide. Loss of oil or oil pressure (hole in case, blown hose, oil pump failure), and governor failure to think of two. All the more reason to check and adjust the prop low pitch stops.. 2,550 to 2,650 static are acceptable, with the lower number (higher static pitch stops angle) giving better glide.

I agree with all of that. I hope the prop shop did that correctly on my CS Whirlwind which uses a McCauley hub which is not adjustable externally if I
understand it correctly.

Also: If I do a full power static runup, rpm should max out at 2550 - 2650 if the low pitch stop is set correctly. I'll check.

 

[Dr_Dave_MT]

You are correct, darn dyslexia!
Thanks for catching that,
Gary

5 out of 3 pilots are dyslexic!

 

[Mel]

5 out of 3 pilots are dyslexic!

Coming from a proud member of D.A.M.............Mothers Against Dyslexia!

 

[Kyle Boatright]

Coming from a proud member of DAM............Mothers Against Dyslexia!

Dyslexics untie!

 

[mfleming]

There are a couple of scenarios where you cannot pull the prop to high pitch/low rpm to extend the glide. Loss of oil or oil pressure (hole in case, blown hose, oil pump failure), and governor failure to think of two. All the more reason to check and adjust the prop low pitch stops.. 2,550 to 2,650 static are acceptable, with the lower number (higher static pitch stops angle) giving better glide.

So I keep hearing about adjusting the low pitch stops. Yesterday I spoke with the tech at Hartzell and asked him about that. I told him on take-off, if I advance the throttle quickly, I hear the governor catch the prop and control the RPM. He said "that is correct, the governor should be controlling the prop on take-off and not the low pitch stops...leave them alone".!

EDIT: I don't know if this is really how we should operate the prop, just passing along Hartzell's recommendation.

 

[Taltruda]

So I keep hearing about adjusting the low pitch stops. Yesterday I spoke with the tech at Hartzell and asked him about that. I told him on take-off, if I advance the throttle quickly, I hear the governor catch the prop and control the RPM. He said "that is correct, the governor should be controlling the prop on take-off and not the low pitch stops...leave them alone".!

EDIT: I don't know if this is really how we should operate the prop, just passing along Hartzell's recommendation.

He’s wrong

 

[BobTurner]

He’s wrong

Yes, he's wrong, but I suspect mflemming is wrong too.

So I keep hearing about adjusting the low pitch stops. Yesterday I spoke with the tech at Hartzell and asked him about that. I told him on take-off, if I advance the throttle quickly, I hear the governor catch the prop and control the RPM. He said "that is correct, the governor should be controlling the prop on take-off and not the low pitch stops...leave them alone".!

EDIT: I don't know if this is really how we should operate the prop, just passing along Hartzell's recommendation.

If you advance the throttle rapidly, and you hear an overspeed for a fraction of a second and then the RPMs settle back, it's probably the governor kicking in and that's not what you want. But if there is no overspeed and settling back, it's likely the low pitch stops being reached, which is what you do want. Experiment: Read in your prop manual which way to turn the allen head bolt at the front of your prop (pull the spinner). Turn it a half turn in the direction to reduce RPM. Repeat the full throttle static run. Did the RPMs go down? If yes, then good, you're on the stops. Restore the setting on that allan head bolt on the prop's front, test that a full power static run gives you about 50 RPM less than red line. Now on an actual take off, does the RPM rise up to red line as you pick up speed? And not go over it? If not adjust the governor.

 

[sailvi767]

It's always interesting to read what pilots get out of their machines, much can be learnt from these pages I Like the last bit, VNE to be in IAS, I still hear pilots say VNE is what's on the dial at high Altitudes, now that's a worry!

Depending on the airframe that may be a correct statement. As a rule for higher performance aircraft like the RV’s it’s not.

 

[rv6ator]

I have always used 1.5 Vso as a target glide speed for most GA aircraft. Using a 55kt Vso that comes out to about 82kts.

 

[Dugaru]

I have always used 1.5 Vso as a target glide speed for most GA aircraft. Using a 55kt Vso that comes out to about 82kts.

And my understanding is that it’s much better to err on the side of too fast rather than too slow.

 

[Mel]

And my understanding is that it’s much better to err on the side of too fast rather than too slow.

Up to a point!

 

[Iluke]

My phase 1 testing yielded a best glide speed of 110 MPH and a minimum sing speed of 80 mph. That said, the curve was relative flat and that 110 is the middle of the flat spot on the curve. I found the same numbers to be about right for Vy and Vx.

That was at about 3,000 feet, about 1650# and with the engine at idle (I'm not brave enough to pull the mixture). I have an O-360 with a FP metal prop

 

[jackking123]

Best Glide is Academic. What do I mean? Best glide (most glide range at given speed) is theoretically MAX L/D, best lift to drag. Great, best glide speed does very with weight, and winds. Best glide according to Van's, 75 and 80 KIAS, 85 to 90 mph. Min sink, not best range is about 70 kts (80 mph). I fly no slower than 100-110 mph (85-105 kts), unless emergency landing strip (field/runway/road) is made, than drag, slips, s-turns come out as needed.**

How are you going to use Best theoretical Glide? Example cruising at 8,500 feet, engine and prop come to abrupt grinding stop, oil covers windscreen. No doubt it is dead. So you bank L & R and look for a place to land nearby and press nearest airport, on your GPS, preferably one with a long runway no obstacles. So depending on winds from 8,500 feet, you will be ON THE GROUND in 13 nautical air miles. You will be on the ground. Subtract 2-3 NM to maneuver. 10 NM. This is were best glide comes in.

Would you REALLY go for an airport 10 NM away, committed? Nice fields to land on directly under or within 5 nm, would that be better? I may ball the plane up in a open field, verses a squeaker 1500 ft down a 5000 ft asphalt runway, but likely I will walk away, wings level, touchdown at min speed. If I try to stretch it for some airport, end up tall.short, over congested area, no good options might be bad, especially if I stall.

LANDING OFF FIELD can be a better choice. I would cut the glide range from 10nm to 1/2 to 3/4. If my GPS says an airport is 10 nm away and might make it I would pass. The "might make it" is the reason, especially with large fields below me.I would rather KNOW I will make it.

BEST GLIDE really critical? Well if off shore and you want to get close to land, yes for sure. You are getting wet regardless, but best to be near the beach than 2 nm out in the ocean.

DOWN LOW Best glide, I do not use, I fly faster to aim point, MONEY IN THE BANK. Extra airspeed I can slip, full flaps to bleed off. When at BEST glide there is no "stretching" it. You go below best glide, your glide distance starts to go down. Yes you can trade some of that airspeed for a transient period, level off momentarily, but than you are really slow and better be ready to land. You have NO EXCESS energy. I like energy in the bank. If you overshoot your landing point, roll off the end of the landing strip/field at 25 kts, that is better than stuffing it in at 60kts short of runway.

** As a CFI, checking people out in a flight clubs new 1965 C-182, I ask pilots to do power off landings from abeam. It was an EYE OPENER. It comes down like a lead balloon. Why? 3-bladed Prop, wind-milling is a lot of drag. (Note there is a trick I have known for 35 yrs, you can try prop in low rpm/high pitch to reduce CS prop drag, it does work on some engine/prop combos. That is another story.)​

​

If I had jumped in this 3 bladed C-182 with no practice and had a real emergency I would not have made my intended landing point. PRACTICE and know your plane. Use what ever speed it takes BUT DON'T GET LOW AND SLOW... Don't stall, don't stall, don't stall. Too many people stalling trying to get to a runway. Off field landings can be excellent, many cases the plane will not be damaged.​

I flew vintage tail wheels 30 years ago, but it's been awhile. I did a flight review for Gent in his BC-12 Taylor-Craft. I'm tail wheel current, flew the BC-12 years ago. It does not slow down, with the residual thrust of the idling engine it was again an eye opener. No flaps all you have is forward slips. I forgot how slippery the Taylor Craft is with no flaps. Again if I flew the Taylor craft with no practice I would over shoot the landing point and whole strip in an emergency, with out practice and currency.​

FIXED pitch props have less drag than constant speed props set to high RPM/Low Pitch. I forgot. Fixed props have more residual thrust in idle than constant speed props. Doing POWER OFF practice with idle is not real world power off. I do not recommend pulling mixture to practice. That is I fly best glide +10 mph at least, may be more (unless it is a Taylor craft).

My suggestion, PICK a glide number and PRACTICE power off landings on occasion in the pattern, near airport at higher altitude, en-route. To endorse a student pilot to solo, as a CFI you have to have student do simulated loss of power on take off, initial climb, pattern, climb/descent/en-route phases. Sadly after their private pilot check ride they many never practice this again.

Besides abeam the number power off landing, which should be easy, I set students up at 1500 ft AGL as if crossing mid field, pull the throttle to idle, and announce "engine failure". The smart students push the throttle back and say engine un-failed. Ha ha. I suggest progressively doing power off landings from progressively further away and higher altitudes. My "go to" is arrive at the touchdown point high, may be 3000 to 6000 feet high, spiral down directly over intended touch down point, breaking out abeam my touch down 1000-1500 feet AGL, and landing like I practice my power offs at home field. It takes out all the guess work. BEST GLIDE DOES NOT FACTOR IN REALLY. I am managing my energy.

Bottom line practice and don't get wrapped up in the number, learn how to fly a forced landing to a runway, or off field. Practice, constantly, not just once every 2 yrs. Memorizing numbers that may not work for you, your airplane, conditions, terrain is not good Prep for a real emergency. I remember MY primary instructor 40 years ago, had me do simulated emergency landings to fields. When I say TO FIELDS, I mean we got down LOW, crossing the fields fence, ditch, tree line, down to 5, 10, 20 feet above the grass or crop or dirt before going around. That visual of what it looked like was both "eye opening" and confidence building. People never see this view low to the ground over un-improved fields. With that said the instructor was constantly blipping the throttle to make sure we had go around power. I just had an instrument student pass his check ride in October. I have not had a primary student in 32 yrs. I retired last year, and only started teaching ratings, and tend to shy away from primary, only doing Flt Reviews, IPC's, Commercial, Instrument, Multi ratings. I forgot how much fun it is teaching students the basics.

 

[Beechx1]

I used to build the flight manual for a certified airplane company. We carefully found best glide speed and then increased the speed until the glide ratio was 90% - 95% of the best ratio. The curve is very flat so it takes a considerable speed increase to reduce the glide ratio. We then added some more for wind (the best glide speed is faster in a headwind) to make it more conservative.

The FAA suggests teaching that you fly best glide speed all the way to the landing site. This is what I started teaching. My students almost always ended up short. After I got my glider rating I started teaching engine out glide the way I was taught to fly a glider. That is to fly best glide speed until you have the field made and then increase speed by 10 - 20 kt. After a couple of attempts, my students almost always landed comfortably on the runway,

The reason this works is that if you end up lower than expected, you can slow down which gives you a temporary boost in glide distance, but also makes your glide more efficient. If you are higher than expected then your drag devices (flaps, slips, controllable prop, etc.) are more effective at killing energy than when you are slow. Also, if you are too fast you will go off the end at a slower than flying speed and zero vertical rate. But if you are too slow, you will land short of the runway at minimum flying speed at best and with a vertical speed down.

Glide speed should be determined in the most adverse (draggy) engine failure condition. This is with the prop at high RPM for constant speed props and windmilling for fixed pitch props. For constant speed props, the procedure should be to reduce RPM as much as possible since this reduces drag and extends the glide. The prop can then be used to add drag and reduce the glide if needed (but usually not by much).

 

[mfleming]

Yes, he's wrong, but I suspect mflemming is wrong too.

If you advance the throttle rapidly, and you hear an overspeed for a fraction of a second and then the RPMs settle back, it's probably the governor kicking in and that's not what you want. But if there is no overspeed and settling back, it's likely the low pitch stops being reached, which is what you do want. Experiment: Read in your prop manual which way to turn the allen head bolt at the front of your prop (pull the spinner). Turn it a half turn in the direction to reduce RPM. Repeat the full throttle static run. Did the RPMs go down? If yes, then good, you're on the stops. Restore the setting on that allan head bolt on the prop's front, test that a full power static run gives you about 50 RPM less than red line. Now on an actual take off, does the RPM rise up to red line as you pick up speed? And not go over it? If not adjust the governor.

He’s wrong

I’m not ready to dismiss the Hartzell factory tech’s advice without something more concrete to compare it against. Do you have a Hartzell manual reference, service document, engineering guidance, or other authoritative source that contradicts what they told us?

 

[Richard Connell]

I’m not ready to dismiss the Hartzell factory tech’s advice without something more concrete to compare it against. Do you have a Hartzell manual reference, service document, engineering guidance, or other authoritative source that contradicts what they told us?

I suspect something’s been lost in translation between you and the tech. The prop is only really on the low pitch stops at
static RPM. theoretically as soon as you are moving the governor takes over. So what he said is right theoretically but only once they come off the stops.
but in reality if your low pitch stops allow too high a static rpm your governor can’t catch the acceleration in rpm quickly enough and you get surging.
I’d suggest the advice above in this thread is correct.

If you’re not comfortable with the advice here (which is totally a sensible view!) then maybe a better approach would be to ask Hartzell where in the manual it says what the tech told you. Because it sounds to me like you definitely got the wrong end of the stick. Here’s the manual.

https://hartzellprop.com/MANUALS/115N-0000-A.pdf

Chapter 5 Inspection and check details the low pitch stop setting. Which is required for all new installations but is frequently overlooked.

Propeller Adjustments

In a recent column for EAA Sport Aviation, contributor Vic Syracuse provides some tips for installing the propeller on your aircraft.

inspire.eaa.org

 

[mfleming]

I suspect something’s been lost in translation between you and the tech. The prop is only really on the low pitch stops at
static RPM. theoretically as soon as you are moving the governor takes over. So what he said is right theoretically but only once they come off the stops.
but in reality if your low pitch stops allow too high a static rpm your governor can’t catch the acceleration in rpm quickly enough and you get surging.
I’d suggest the advice above in this thread is correct.

If you’re not comfortable with the advice here (which is totally a sensible view!) then maybe a better approach would be to ask Hartzell where in the manual it says what the tech told you. Because it sounds to me like you definitely got the wrong end of the stick. Here’s the manual.

https://hartzellprop.com/MANUALS/115N-0000-A.pdf

Chapter 5 Inspection and check details the low pitch stop setting. Which is required for all new installations but is frequently overlooked.

Propeller Adjustments

In a recent column for EAA Sport Aviation, contributor Vic Syracuse provides some tips for installing the propeller on your aircraft.

inspire.eaa.org

I don’t think anything was lost in translation. That was exactly the issue I asked Hartzell about, and the advice I received was not to adjust the low pitch stops.

Having now read that section of the manual more carefully, I agree there’s something worth clarifying. My next step is to go back to Hartzell and ask how their advice lines up with the manual language, rather than guessing at which interpretation is correct.

 

[Richard Connell]

I don’t think anything was lost in translation. That was exactly the issue I asked Hartzell about, and the advice I received was not to adjust the low pitch stops.

Having now read that section of the manual more carefully, I agree there’s something worth clarifying. My next step is to go back to Hartzell and ask how their advice lines up with the manual language, rather than guessing at which interpretation is correct.

Then I think it’s pretty clear whoever you spoke to was wrong. This isn’t some grey area of prop/engine/governor setup. Fine pitch stop setting is a well understood and simple process - that’s also explicitly outlined in the manual.
All that will happen now is that the next person who googles it will get an AI answer saying “some people at Hartzell say to not change the low pitch stops” because of this thread.
Said in jest - but sadly think there’s some truth to it

 

[mfleming]

Then I think it’s pretty clear whoever you spoke to was wrong. This isn’t some grey area of prop/engine/governor setup. Fine pitch stop setting is a well understood and simple process - that’s also explicitly outlined in the manual.
All that will happen now is that the next person who googles it will get an AI answer saying “some people at Hartzell say to not change the low pitch stops” because of this thread.
Said in jest - but sadly think there’s some truth to it

I think you may be stating this with more certainty than the facts support.

I agree the manual contains a low pitch stop procedure, and I agree the manual is the controlling reference. What I do not agree with is the leap from that to “whoever you spoke to was wrong” without knowing exactly what context Hartzell was considering.

There are several possible explanations: the tech may have misspoken, I may have misunderstood the context, or Hartzell may be giving practical field advice that is more conservative than simply “the manual contains an adjustment procedure.” For example, they may be trying to prevent people from using the low pitch stop to chase an RPM issue that is really governor, rigging, engine power, tach, or installation related.

So yes, the manual procedure matters. But I’m not going to dismiss a Hartzell tech with substantial propeller-shop experience based solely on forum certainty. I’m going to ask Hartzell to reconcile the manual language with the advice I was given.

 

[Richard Connell]

I think you may be stating this with more certainty than the facts support.

I agree the manual contains a low pitch stop procedure, and I agree the manual is the controlling reference. What I do not agree with is the leap from that to “whoever you spoke to was wrong” without knowing exactly what context Hartzell was considering.

There are several possible explanations: the tech may have misspoken, I may have misunderstood the context, or Hartzell may be giving practical field advice that is more conservative than simply “the manual contains an adjustment procedure.” For example, they may be trying to prevent people from using the low pitch stop to chase an RPM issue that is really governor, rigging, engine power, tach, or installation related.

So yes, the manual procedure matters. But I’m not going to dismiss a Hartzell tech with substantial propeller-shop experience based solely on forum certainty. I’m going to ask Hartzell to reconcile the manual language with the advice I was given.

I don’t think anything was lost in translation. That was exactly the issue I asked Hartzell about, and the advice I received was not to adjust the low pitch stops.

Having now read that section of the manual more carefully, I agree there’s something worth clarifying. My next step is to go back to Hartzell and ask how their advice lines up with the manual language, rather than guessing at which interpretation is correct.

That's why I qualified my original statement with the "lost in translation".

Youre right, we don't know exactly what you asked, and exactly what he told you - but you explicitly stated you are adamant that nothing was lost in translation and Hartzell told you to not touch the low pitch stops.

Im confident that when you clarify things with Hartzell the advice will match the manual.