VG’s on my Ovation 2

[Steve Yucht]

I’ve been waiting 3 years to get a no wind day here in FL to report about the effects of my VG’s on cruise speed. Everyone says that you loose top end speed in cruise except for the folks who make them. They believe that it’s a negligible loss. I bought my plane with them on so have nothing to compare to. I definitely have a significantly reduced stall speed of at most 55 kts and it’s hard to get her to stall. Back to today, I was at 7000 ft running 100 degrees ROP  23.3 inches of MP, 2400 RPM and had a TAS of 174 kts. Book speed is 175 kts. See pic’s below.  I hope this helps anyone thinking about VG’s. 

[Alan Maurer]

I was flying South from Panama City to Venice on Friday in mid morning at 7000 feet with same settings and 4 kt tail wind (which does not changeTAS and I took a photo of my TAS. See photo below. Also Ovation 2 M20R. I do not have VG's.

[Mooney Dog]

On 5/14/2022 at 4:08 PM, Steve Yucht said:

had a TAS of 174 kts. Book speed is 175 kts

THATS 1 WHOLE KNOT OF SPEED YOU'RE LOSING THERE MAN! WHAT ARE YOU DOING! 

 

On a more serious note. You're probably losing a bit of speed. There was a study done on a bonanza some years ago which showed around 3% loss of speed with VGs installed. 

Here's a link to the full thing.

https://www.nar-associates.com/technical-flying/vortex/Vgs_cruise_wide_screen.pdf

Edited May 16, 2022 by Mooney Dog
added more info

[ArtVandelay]

I get 7 knots or more difference in my TAS because of weather conditions. Comparing to book numbers or others is a futile exercise.

[Schllc]

There are so many variables, not just related to vg’s but general plane rigging, trueness, weight, etc  that drilling down that close is really difficult. 
I’ll tell you this though, I’ve had a few ovations, and 191kts TAS was not typical at any altitude or power setting. 
Alan must have one of those magic O’s. 
Hang on to that one!!!

[Steve Yucht]

Alan, you definitely found the magic there!  What was your GS at the time?

[A64Pilot]

VG’s have their purpose, they are good for aircraft that often fly at high angles of attack, I had them on my Maule and worked with Annie Brogan to get them on our crop duster type certificate, she flew down with her DER test pilot, I supplied the aircraft and conformity inspection, she did the rest. Reason to put it on the TC is many countries don’t accept US STC’s, but do the TC of course, and VG’s do some good on crop dusters, good bang for the buck.

Anyway in my opinion VG’s aren’t maybe the best choice for airplanes who’s mission is cross country where speed is desirable. VG’s are sort of like bushwheels, great if you need them, not so much if you don’t. I can’t imagine needing them on my Mooney, the Maule sure.

My testing showed they didn’t do much for stall speed reduction, they did of course increase critical angle of attack, but at stall your at an airspeed of diminishing returns angle of attack wise, meaning it takes a lot of angle of attack to make much speed difference. On the Maule they did improve aileron authority at slow speeds, something that a Maule has trouble with, and I believe a lot of STOL aircraft too, so VG’s can have effects other than just increasing critical angle of attack.

You’ll see VG’s on Commercial aircraft where they have separation that needs fixing, but it’s not common to see them full span, you will even see them underneath the slats which is neat as they are in airflow when the slats are deployed, but not when they are retracted.

VG’s work by energizing the boundary airflow layer. That energy of course comes from the aircraft in the form of drag.

‘Now it’s possible that on some aircraft that have separation problems that the drag reduction that comes from keeping the airflow more attached may outweigh the drag created from energizing the airflow and you have an overall reduction in drag. But we are supposed to be a laminar flow wing, so we shouldn’t have flow separation problems.

Edited May 17, 2022 by A64Pilot

[kevinw]

22 hours ago, Schllc said:

There are so many variables, not just related to vg’s but general plane rigging, trueness, weight, etc  that drilling down that close is really difficult. 
I’ll tell you this though, I’ve had a few ovations, and 191kts TAS was not typical at any altitude or power setting. 
Alan must have one of those magic O’s. 
Hang on to that one!!!

The 2-Blade McCauley prop on the Ovation 2 gave it the fastest cruise speed but the longest ground roll on takeoff. I'm replacing my 3-blade McCauley on my Ovation with the Hartzell Top Prop F7498 as part of the 310hp STC. I haven't picked it up yet but I read here on MS that I could gain 10 knots over my McCauley 3-blade (which is listed for sale in the parts page). I true out at 180 @ 7-8000 ft, 2400 rpm now so time will tell if I can get it to 190. Seems too good to be true but I'm hopeful.

[Cruiser]

"I feel the need... the need for speed" 

[carusoam]

Things that go well together….

Short field…

AOAi…

VGs….

Cruise at altitude….

Good speed control…

-a-

[A64Pilot]

16 hours ago, kevinw said:

The 2-Blade McCauley prop on the Ovation 2 gave it the fastest cruise speed but the longest ground roll on takeoff. I'm replacing my 3-blade McCauley on my Ovation with the Hartzell Top Prop F7498 as part of the 310hp STC. I haven't picked it up yet but I read here on MS that I could gain 10 knots over my McCauley 3-blade (which is listed for sale in the parts page). I true out at 180 @ 7-8000 ft, 2400 rpm now so time will tell if I can get it to 190. Seems too good to be true but I'm hopeful.

My SWAG is the 10 kts if real will come from increased HP, not prop, I can’t see 10 kts from a prop unless original was a really horrible mismatch.

Props are often optimized for the speed the aircraft operates, float plane props for instance are good stump pullers, but don’t work well at speed.

For instance one of the crop dusters we built used a Garret -10 (1000 HP) engine in place of the 750 HP -34 Pratt, I believe the engine was originally an MU-2 engine, the backwards turning one, anyway the same prop was used as the MU-2 so it’s performance while better wasn’t as good as it could have been, the crop duster just wasn’t capable of the speeds the prop would work best at. 

[kevinw]

On 5/18/2022 at 8:25 AM, A64Pilot said:

My SWAG is the 10 kts if real will come from increased HP, not prop, I can’t see 10 kts from a prop unless original was a really horrible mismatch.

Props are often optimized for the speed the aircraft operates, float plane props for instance are good stump pullers, but don’t work well at speed.

For instance one of the crop dusters we built used a Garret -10 (1000 HP) engine in place of the 750 HP -34 Pratt, I believe the engine was originally an MU-2 engine, the backwards turning one, anyway the same prop was used as the MU-2 so it’s performance while better wasn’t as good as it could have been, the crop duster just wasn’t capable of the speeds the prop would work best at. 

My mechanic told me the top prop is simply a more efficient prop than the McCauley and that I should see a little increase in cruise, but not 10 knots. After about 10 hours I can say he was right; I'm seeing 3-4. On the flight home I thought it was more like 6 but that must have been a good day. I previously trued out at 178-179 and now I'm 182ish with the same power settings. One thing I didn't expect is the new prop seems to slow the plane down by creating a little more drag at idle. I was doing power off 180s the last few days and noticed I don't glide quite as well and have to make my turn sooner.

[StevenL757]

On 5/17/2022 at 4:25 PM, kevinw said:

The 2-Blade McCauley prop on the Ovation 2 gave it the fastest cruise speed but the longest ground roll on takeoff. I'm replacing my 3-blade McCauley on my Ovation with the Hartzell Top Prop F7498 as part of the 310hp STC. I haven't picked it up yet but I read here on MS that I could gain 10 knots over my McCauley 3-blade (which is listed for sale in the parts page). I true out at 180 @ 7-8000 ft, 2400 rpm now so time will tell if I can get it to 190. Seems too good to be true but I'm hopeful.

Unfortunately, you won't get 10kts switching to the F7498 (Acclaim Type-S) prop.  You might manage 6 knots max.  If you have TKS, it'll be closer to 4 knots' increase.  The major payoffs for the F7498 are shortened takeoff run, excellent climb performance, and the speed increase at cruise.

Also, your target RPM at ALL altitudes except takeoff and landing with the 310HP STC should be 2550, not 2400.  This coming from the person who designed the STC and with whom I've worked in the course of flight-testing to verify these numbers...on two different Ovations I've owned...both with 310 upgrades and F7498 props.  2400RPM does nothing to reduce any wear appreciably.  Some argue sound reduction is a justification for pulling back lower thana 2550, but it's negligible, and not a sufficient argument in my opinion.  2550 is the sweet spot.  Your flow should be:

• Takeoff at 2700RPM
• Once cleaned up and out of 1000AGL, pull back to 2550 and leave it there
• Adjust MAP to 23"
• As you climb above about 8,000 and MP starts to drop, increase MAP to full power and leave it there
• When you reach cruise, adjust fuel for 40-50 degrees' LOP and leave it there

Unless you need to reduce speed for turbulence, the Ovation should be flown with these settings.  This is one of the surefire ways to make TBO on your IO550G (with upgrade) or IO550N on the Ovation.

I won't start the LOP/ROP debate, but I'd consider switching to LOP, as the 180KTAS at 2400RPM numbers you're giving don't sound in-line with LOP operations.  Your tuned-induction engine is designed to fly very efficiently at LOP, whereas many others on here may be better at ROP.  This coming from Bob Kromer, factory test pilot and engineer...whom many here have heard speak on the topic.

In contrast, I'm witnessing a guy's engine in annual right now who recently purchased an Ovation where the previous owner flew it for around 1200 hours...about 900 of those on a factory reman engine...all at LOP.  When the airplane was turned over to the new owner, it was running at peak performance.  Fast-forward about 90 hours (all of them flown by the new owner ROP), he's facing 3 bad cylinders...all chalked up to ROP operations according to his mechanic.

So, assuming you follow the above, your realistic expectation with your new F7498 with 310STC should be in the ballpark of 176KTAS (without TKS), and 173-174KTAS (with TKS).  So, while I respect the folks in the "Mike Busch says..." camp, and others with their theories on how they think these engines should be operated, I've worked with - and continue to follow the advice - of the folks who actually established the parameters for long engine life on the Ovation platform...one of them being a patent holder on the original design of the 550 platform.  After observing operations at each end of the spectrum...in my airplanes and several others over the last 13 years...I'd highly encourage Ovation owners to take it to heart and switch your operating habits if you aren't already doing so above.

Sorry for the long note...just wanted to reiterate something for the sake of consistency and best-practices that has served me well over the years.

[kevinw]

21 minutes ago, StevenL757 said:

Unfortunately, you won't get 10kts switching to the F7498 (Acclaim Type-S) prop.  You might manage 6 knots max.  If you have TKS, it'll be closer to 4 knots' increase.  The major payoffs for the F7498 are shortened takeoff run, excellent climb performance, and the speed increase at cruise.

Also, your target RPM at ALL altitudes except takeoff and landing with the 310HP STC should be 2550, not 2400.  This coming from the person who designed the STC and with whom I've worked in the course of flight-testing to verify these numbers...on two different Ovations I've owned...both with 310 upgrades and F7498 props.  2400RPM does nothing to reduce any wear appreciably.  Some argue sound reduction is a justification for pulling back lower thana 2550, but it's negligible, and not a sufficient argument in my opinion.  2550 is the sweet spot.  Your flow should be:

• Takeoff at 2700RPM
• Once cleaned up and out of 1000AGL, pull back to 2550 and leave it there
• Adjust MAP to 23"
• As you climb above about 8,000 and MP starts to drop, increase MAP to full power and leave it there
• When you reach cruise, adjust fuel for 40-50 degrees' LOP and leave it there

Unless you need to reduce speed for turbulence, the Ovation should be flown with these settings.  This is one of the surefire ways to make TBO on your IO550G (with upgrade) or IO550N on the Ovation.

I won't start the LOP/ROP debate, but I'd consider switching to LOP, as the 180KTAS at 2400RPM numbers you're giving don't sound in-line with LOP operations.  Your tuned-induction engine is designed to fly very efficiently at LOP, whereas many others on here may be better at ROP.  This coming from Bob Kromer, factory test pilot and engineer...whom many here have heard speak on the topic.

In contrast, I'm witnessing a guy's engine in annual right now who recently purchased an Ovation where the previous owner flew it for around 1200 hours...about 900 of those on a factory reman engine...all at LOP.  When the airplane was turned over to the new owner, it was running at peak performance.  Fast-forward about 90 hours (all of them flown by the new owner ROP), he's facing 3 bad cylinders...all chalked up to ROP operations according to his mechanic.

So, assuming you follow the above, your realistic expectation with your new F7498 with 310STC should be in the ballpark of 176KTAS (without TKS), and 173-174KTAS (with TKS).  So, while I respect the folks in the "Mike Busch says..." camp, and others with their theories on how they think these engines should be operated, I've worked with - and continue to follow the advice - of the folks who actually established the parameters for long engine life on the Ovation platform...one of them being a patent holder on the original design of the 550 platform.  After observing operations at each end of the spectrum...in my airplanes and several others over the last 13 years...I'd highly encourage Ovation owners to take it to heart and switch your operating habits if you aren't already doing so above.

Sorry for the long note...just wanted to reiterate something for the sake of consistency and best-practices that has served me well over the years.

Thanks for all the information. I was just commenting on this post a little while ago indicating that I'm seeing a 3-4 knot increase, no where near 10. I do not have TKS and now see 182-183 kias with my 24/24 power setting.

I appreciate your insight on power settings and LOP/ROP operations. I've asked a few people if I should pull the RPMs back to 2550 during climb; one told me yes and another said to leave it at 2700 all the way up to cruise altitude. I've always been open to running LOP but just never felt comfortable trying it. I have two questions for you: When running LOP does it matter what altitude you're flying at? i.e. Does the engine perform well on short flights at lower altitudes such as 5,000'? Second, at what point do you start enriching the mixture as you reach your destination? Before or during decent?

I guess if the entire LOP procedure was clearly explained I would be more comfortable with it. I have a JPI EDM 900 in my panel so getting to LOP should be easy. I should probably run a gami lean test just to make sure my engine can run LOP.

Thanks for taking the time to post this. I will certainly refer back to it.

Kevin

[LANCECASPER]

45 minutes ago, kevinw said:

Thanks for all the information. I was just commenting on this post a little while ago indicating that I'm seeing a 3-4 knot increase, no where near 10. I do not have TKS and now see 182-183 kias with my 24/24 power setting.

I appreciate your insight on power settings and LOP/ROP operations. I've asked a few people if I should pull the RPMs back to 2550 during climb; one told me yes and another said to leave it at 2700 all the way up to cruise altitude. I've always been open to running LOP but just never felt comfortable trying it. I have two questions for you: When running LOP does it matter what altitude you're flying at? i.e. Does the engine perform well on short flights at lower altitudes such as 5,000'? Second, at what point do you start enriching the mixture as you reach your destination? Before or during decent?

I guess if the entire LOP procedure was clearly explained I would be more comfortable with it. I have a JPI EDM 900 in my panel so getting to LOP should be easy. I should probably run a gami lean test just to make sure my engine can run LOP.

Thanks for taking the time to post this. I will certainly refer back to it.

Kevin

If you have Tempest Fine Wire plugs you should be able to run LOP easily with or without GAMIs due to the excellent induction system on the IO-550.

[StevenL757]

59 minutes ago, kevinw said:

Thanks for all the information. I was just commenting on this post a little while ago indicating that I'm seeing a 3-4 knot increase, no where near 10. I do not have TKS and now see 182-183 kias with my 24/24 power setting.

I appreciate your insight on power settings and LOP/ROP operations. I've asked a few people if I should pull the RPMs back to 2550 during climb; one told me yes and another said to leave it at 2700 all the way up to cruise altitude. I've always been open to running LOP but just never felt comfortable trying it. I have two questions for you: When running LOP does it matter what altitude you're flying at? i.e. Does the engine perform well on short flights at lower altitudes such as 5,000'? Second, at what point do you start enriching the mixture as you reach your destination? Before or during decent?

I guess if the entire LOP procedure was clearly explained I would be more comfortable with it. I have a JPI EDM 900 in my panel so getting to LOP should be easy. I should probably run a gami lean test just to make sure my engine can run LOP.

Thanks for taking the time to post this. I will certainly refer back to it.

Kevin

My pleasure, and you're very welcome.  See if I can hit your points above...

• "Can" you leave the power all the way up to 2700 all the way to cruise?
  • Yes; however, you'll see notably higher CHTs most of the way up.  On hotter days, this will be exacerbated, and you'll likely be well over 400F on at least one or more cylinders until you push the nose down and get more air flowing over the baffles.  Pulling back to 2550 will reduce these CHTs in the climb...both in hot and cold weather.  Keeping your climb-out speeds in hot weather to 130-135KIAS will help cool things down.  "Cruise-climb" is another of your cylinders' friends.
• "Should" you leave the power at 2700RPM all the way up?
  • No.
• When running LOP, it generally doesn't matter at what altitude you're flying.  I say "generally" only because in Maine (for example) during Fall/Winter, when temps at altitude are around, say -20C or colder (rough estimate), those temps are cold-enough to where LOP operations drop CHTs to the 250F mark.  When I see that trending, I switch to ROP to keep the cylinders warmer than 250F - which should be your minimum CHT at any time.  When I have the cold weather plate installed in front of the oil cooler, I have a little more latitude, but generally end up going ROP in extreme cold temps in cruise.
• When do I start enriching?  During descent.  I generally monitor the %LOP reading on my EDM930, and will enrich to maintain that throughout most of the descent and my Approach checklist.  Then,  I'll generally enrich to the "dark blue" area on my EGT bars (1400F-1450F) until I need to pull back power any more for the approach.

Your IO550 can certainly run LOP without GAMIs.  I've had two sets of the stock Continental injectors on my airplanes, and although I've seen a split of around 20'ish degrees (more than I'd like), the stock injectors have been acceptable, and not worth pulling in lieu of GAMIs.  If a time comes where I see a 25-degree split or greater consistently at altitude, and I know that I don't have a partially-clogged injector, then I'll consider GAMIs.

Bottom-line is that finding someone who can fly in your right seat, and work with you to manage your engine LOP is an extremely valuable experience.  I highly recommend doing this at your earliest opportunity.  Certainly hope this helps.

Steve