Flaps Up Stall Speed and Hot Oil Temps

[asw20c]

I'm firmly in Phase 1 testing having only about 10 hours on my -14A as of today. My cylinder head temperatures came down nicely within only 2-3 hours, and although my oil temps have also come down, that isn't saying much because they were at redline for the first few hours. Now they tend to hover around 220; far hotter than I would like, but at least not redline. Yes, I've checked my baffling and as far as I am able to determine it is perfect. I also don't have any obstructions to the oil cooler. I even tried taping off my heater inlet so as not to be "robbed" of a few square inches of inlet air (it made no difference). The only options I see left are to just keep flying since Lycoming says engine break-in can take 50 hours or more. My other thought is to try retarding the spark advance if the temps aren't down by around my first oil change. My home field is at 6200 feet, so I have been flying at pattern altitude for much of the break-in, around 7500 feet. That usually puts me at around ~23" manifold pressure and 2700 RPM. I'll occasionally dial it back to cruise RPM of 2450, just for some variation. Any other thoughts are welcome.

As for my flaps up stall speed, I'm having trouble nailing it down. When straight and level with the ball centered and the flaps up, it simply won't stall. It will buffet and establish a high sink rate, but it won't stall. I have to be at half or more flaps before it breaks and drops a wing. My empty weight is 1268 and I've tried testing at different all-up weights and with as much as 120 lbs in the baggage area. When the baggage area is empty, by CG is between 83" and 84". With 120 lbs in the baggage area the CG moves back to around 86"+. I can't put enough weight in the baggage area to reach the aft CG, so I'm normally going to be somewhere in the forward 1/3. As far as I can tell, the published flaps up stall speed looks about right. Anyone have a similar experience?

And just a few data points and some motivation for those still building, the pitot/static system is very accurate per my tests and calculations. Additionally, I installed the red cube per the plans and my fuel totalizer is also dead nuts on. No kidding. It wasn't even a tenth of a gallon off after burning 43 out of 50 gallons. I'm also seeing solid true airspeeds of 180-186 knots in level flight at full power settings (~13.3 gal/hr, ~23" and 2700 RPM). Very impressive!

 

[Toobuilder]

Any other thoughts are welcome.

Install a viscosity valve. This action will rule out any poorly sealing or operating vernatherm.

 

[dmattmul]

I'm firmly in Phase 1 testing having only about 10 hours on my -14A as of today. .

As for my flaps up stall speed, I'm having trouble nailing it down.

Why are you slowing your 14A down inviting high oil temps and CHT's??? Oil temps need to be below 200 F. You will have plenty of time later on in phase 1 to test stall characteristics. Also, you are only at 1,300 AGL, a little low to be testing stalls in a new airframe?

 

[PilotjohnS]

As far as stall is concern, see if the Garmin ESP is limiting pitch up attitude. I had to disable ESP during stall and Vx testing because deck angle got too great.

 

[Reflex]

I'm certainly no expert, but aren't you concerned about your altitude for break in? I just ran a quick check and it appears that the density altitude at which your flying this time of year could far exceed that recommended by Lycoming (assuming you have a Lycoming IO-390). As I recall, Lycoming recommends at maximum density altitude of 6500 feet during break in so that that 70 - 75% power can be achieved.

Not sure if this has anything to do with your oil temps....but it may. I know it's tough to be patient, but given the amount of work and money we put into these contraptions, would it not be better to wait until late fall or winter will proper density altitudes could be used?

Also, wondering about the scat tube between the baffle and the oil cooler, that round to square transition at the oil cooler is a good place for leakage and/or poor air flow.

Best of luck,

Fred

 

[Desert Rat]

"...it simply won't stall. It will buffet and establish a high sink rate, but it won't stall..."

It may not be dropping the nose, but what you're describing is definitely a stall. I can make a lot of airplanes behave this way depending on gross weight, density altitude, power setting and where the cg is.

It would be easier to do this with the Garmin babysitter off, but either way you should still be able to use your big boy muscles to overcome its desire to save you from yourself.

 

[Desert Rat]

Hey also, regarding your oil temp.


I'm in about the same place as you with phase 1, with an IO390 in an RV7, but I've got the benefit of being down in the flatlands.

At 25/25 power settings I'm seeing oil temps about 140 degrees F above OAT in cruise flight. I'm currently tweaking baffle seals etc to try to get this down a bit, and I'm only flying during the mornings when it's relatively cool out.

I did a couple of stalls on the 2nd or 3rd flight to see how it would behave and in the slow flight/approach to stall the oil temp shot up to the hight 220's. I'm deferring the stall test card until later in phase one when I'm sure I've got the engine broken in and/or the temps come down. I have zero interest in doing an hour long flight with oill temps that high just because it happens to be the next page number in the test card binder.

 

[Ironflight]

For your stall, what pitch rate are you using in the approach to the stall? Often-times, I find aircraft will mush into a stalled/falling leaf condition if I use to low of a pitch rate. Try pulling a little more ”briskly” into the stall and see what you get (just don‘t be so aggressive that you end up in a tail slide!).

 

[DanH]

I'm firmly in Phase 1 testing having only about 10 hours on my -14A as of today. My cylinder head temperatures came down nicely within only 2-3 hours, and although my oil temps have also come down, that isn't saying much because they were at redline for the first few hours. Now they tend to hover around 220; far hotter than I would like, but at least not redline. Yes, I've checked my baffling and as far as I am able to determine it is perfect. I also don't have any obstructions to the oil cooler. I even tried taping off my heater inlet so as not to be "robbed" of a few square inches of inlet air (it made no difference). The only options I see left are to just keep flying since Lycoming says engine break-in can take 50 hours or more. My other thought is to try retarding the spark advance if the temps aren't down by around my first oil change. My home field is at 6200 feet, so I have been flying at pattern altitude for much of the break-in, around 7500 feet. That usually puts me at around ~23" manifold pressure and 2700 RPM. I'll occasionally dial it back to cruise RPM of 2450, just for some variation. Any other thoughts are welcome.

Let's start by saying reports of high oil temperature are rather common with the 14A, or the 14 for that matter. Which version (original or dual outlet w/cowl flap) are you flying?

You're apparently running 2700 to keep rated power at 80% or better at 7500 ft. Lycoming expresses the desired break-in parameter as a percent of rated power, because pilots understand the term. However, the real goal for break-in operation is high cylinder pressure to push the compression rings out against the cylinder wall.

Think of it this way...horsepower is (torque x RPM) / 5252, while torque is fundamentally cylinder pressure. Max torque (i.e. cylinder pressure) for a standard Lycoming is down around 2400. Power is higher at 2700 only because of the RPM multiple. Although rated power is less at 2400, cylinder pressure is the same, or higher.

Ok, so here we have a heating problem. Cooling demand is proportional to engine mass flow, which in our case means RPM. More RPM also increases frictional heating. So pull back on RPM and see what it does for oil temperature. If breaking a Lycoming rule is somehow bothersome, note the difference in power would only be about 7%.

Still bothersome? Ok, how might you further increase cylinder pressure at a lower RPM?

First, the obvious, use a lower altitude.

Use more speed to boost dynamic pressure, i.e. wheel pants and other drag reductions in place.

Use best power mixture....which is not full rich, in particular when at 7500 ft.

Add ignition advance. Gotta be careful here, as it can serious spike pressures. You mentioned ignition advance. What setup are you flying now?

 

[asw20c]

Let's start by saying reports of high oil temperature are rather common with the 14A, or the 14 for that matter. Which version (original or dual outlet w/cowl flap) are you flying?

You're apparently running 2700 to keep rated power at 80% or better at 7500 ft. Lycoming expresses the desired break-in parameter as a percent of rated power, because pilots understand the term. However, the real goal for break-in operation is high cylinder pressure to push the compression rings out against the cylinder wall.

Think of it this way...horsepower is (torque x RPM) / 5252, while torque is fundamentally cylinder pressure. Max torque (i.e. cylinder pressure) for a standard Lycoming is down around 2400. Power is higher at 2700 only because of the RPM multiple. Although rated power is less at 2400, cylinder pressure is the same, or higher.

Ok, so here we have a heating problem. Cooling demand is proportional to engine mass flow, which in our case means RPM. More RPM also increases frictional heating. So pull back on RPM and see what it does for oil temperature. If breaking a Lycoming rule is somehow bothersome, note the difference in power would only be about 7%.

Still bothersome? Ok, how might you further increase cylinder pressure at a lower RPM?

First, the obvious, use a lower altitude.

Use more speed to boost dynamic pressure, i.e. wheel pants and other drag reductions in place.

Use best power mixture....which is not full rich, in particular when at 7500 ft.

Add ignition advance. Gotta be careful here, as it can serious spike pressures. You mentioned ignition advance. What setup are you flying now?

Dan, that was helpful. I'm using the default advance as it came from the factory. Dual P-Mag, Thunderbolt YIO-390-EXP340, dual outlet cowling with cowl flap. I have been flying as low as I dare (usually around 7500 feet, but still get terrain warnings here in the high desert), in the mornings only when it is still cool out.

I have a bigger problem now though besides high oil temps. On this morning's flight, my prop governor went wonky on me. Wouldn't hold an RPM, then would overspeed, then no adjustment possible. I had to abort my flight and head home, being mindful of the throttle to avoid overspeeding the prop. I took the top cowl off afterward to see if anything came loose on the governor but everything looks perfect. No nuts have worked loose, the linkage is still correct and hits the stops at both ends. No oil leaks. Therefore it looks like something inside has gone wrong. What a pain it's going to be to remove if I have to send it in for warranty work. I had about 5.2 quarts in the sump at the end of the flight. I'm finding that if I put more than 6 quarts in that it just gets dumped overboard. I mention this because I thought maybe the prop governor might not work properly if it was low on oil, but that should be plenty for safe operation. Only 12 hours into phase 1 and I'm grounded. This stinks!

 

[Jjackh10]

Dan, that was helpful. I'm using the default advance as it came from the factory. Dual P-Mag, Thunderbolt YIO-390-EXP340, dual outlet cowling with cowl flap. I have been flying as low as I dare (usually around 7500 feet, but still get terrain warnings here in the high desert), in the mornings only when it is still cool out.

I have a bigger problem now though besides high oil temps. On this morning's flight, my prop governor went wonky on me. Wouldn't hold an RPM, then would overspeed, then no adjustment possible. I had to abort my flight and head home, being mindful of the throttle to avoid overspeeding the prop. I took the top cowl off afterward to see if anything came loose on the governor but everything looks perfect. No nuts have worked loose, the linkage is still correct and hits the stops at both ends. No oil leaks. Therefore it looks like something inside has gone wrong. What a pain it's going to be to remove if I have to send it in for warranty work. I had about 5.2 quarts in the sump at the end of the flight. I'm finding that if I put more than 6 quarts in that it just gets dumped overboard. I mention this because I thought maybe the prop governor might not work properly if it was low on oil, but that should be plenty for safe operation. Only 12 hours into phase 1 and I'm grounded. This stinks!

You may want to look for a recent thread here about setting you prop pitch stops. Set properly you won't overspeed.

 

[Toobuilder]

You may want to look for a recent thread here about setting you prop pitch stops. Set properly you won't overspeed.

Correctly set pitch stops will not prevent an overspeed in the air, unfortunately. Not if the governor fails to provide oil to the prop.

Regarding the latest governor issues with the OP, I suffered a similar condition at 4.9 SMOH on the Rocket. The governor would not hold, so readjusted and it overshot the other way, then went straight into major overspeed. Prop went flat (against the pitch stops), but at WOT and 200+ knots that meant 4900 RPM before I could get the throttle back and slow the airplane. Turns out the governor drive shaft sheared internally and quit governing. The resulting uncontrollable torsional vibration broke the crank, prop hub, and safety wire holding 4 of the 6 prop bolts - those 4 bolts also backed out several turns.

Suggest you pull the governor and see if it still functions. And regarding your overspeed, how high did you go? Your next call might be your insurance company.

 

[Carl Froehlich]

Dan, that was helpful. I'm using the default advance as it came from the factory. Dual P-Mag,

What does ”default” mean??

Before doing anything else I suggest verifying the timing jumper is installed in each pMag. The IO-390 does not like the more aggressive jumper out timing advance curve.

Carl

 

[DanH]

Dan, that was helpful. I'm using the default advance as it came from the factory. Dual P-Mag,

Does "default setting" mean timing set at TDC and no jumper between terminals 2 and 3?

I had about 5.2 quarts in the sump at the end of the flight. I'm finding that if I put more than 6 quarts in that it just gets dumped overboard. I mention this because I thought maybe the prop governor might not work properly if it was low on oil, but that should be plenty for safe operation. Only 12 hours into phase 1 and I'm grounded. This stinks!

Opinions vary, but in my 390 experience 5.2 quarts is not enough. I see a higher oil temperature as I drop to six quarts or less.

No doubt you've been blowing some out the breather. All Lycomings lose more oil out the breather prior to full break-in, particularly early in the process. Rings leak until seated; that's the point. Blow-by is the source of the air carrying oil droplets out the breather fitting. Later, blow-by should be significantly less (oil burn too), so run six to seven.

Yeah, I know, a C/D/119 model has a seven quart sump. I don't think that was a good idea either, but Williamsport didn't ask what I thought.

The big angle valve is partially oil cooled, more so than a typical parallel valve. The 390 will maintain workable oil pressure at very low sump levels, but as noted previously, you may see a temperature rise as the volume is reduced. The likely reason is entrained air, in particular at 2700 RPM. At that speed, oil is circulating at roughly 7 gallons per minute...so at 5.5 quarts, it's circulating the entire sump volume every 12 seconds. As oil squeezes out of the spaces between the bearings and journals, and as it is sprayed on the back of the pistons, it gets flailed and slung by the rotating crank assembly until it finally lands on the case walls with lots of entrained air bubbles.

The classic oil de-aerator is a flat sheet of material in the top of an oil tank, As the return oil is dumped on the surface, air bubbles easily escape from the thin layer. Now consider the design of the Lycoming case. There is certainly more than one reason for its overall shape and detailing. However, consider what happens as oil full of air bubbles lands on the walls, then runs down and across the large flat areas (yellow) on the way to the little slot (red) leading to the sump. In the sump, air rises, while the pump feed is at the bottom. The sump is quite shallow, so small changes in depth mean more or less air in the into the pump feed.

Drop to 2400 RPM and you have a 12% slower flow rate, 12% fewer combustion events, and the Bass-O-Matic is spinning slower...less air entrainment:

 

[D-Dubya]

I remember the Bass-O-Matic!!! I was in high school when that was originally on SNL...my friends and I laughed so hard that night when their "ad" ran. Still funny after forty-something years. Maybe not as good as Massive Head Wound Harry, but still a good one.

Regarding the govna' going belly up, my governor also quit working with only a few hours on the plane in Phase 1. Don't know if it injected some crud from the new installation, the seals dried out from sitting in my garage too long (that's a whole 'nuther story), or something else. I took it to a prop shop so they could clean it up and replace all the O-rings and seals. They bench tested it and everything worked fine after that. Just part of the joy and excitement of owning an aircraft.

 

[Toobuilder]

Before doing anything else I suggest verifying the timing jumper is installed in each pMag. The IO-390 does not like the more aggressive jumper out timing advance curve.

Jumper installed, AND a mechanical retard on the housing to back it off a bit more.

 

[SkyDweller]

Just posting to reinforce what some others have said.

I have a 9A with an IO-320 and dual Emag 114’s. I struggled with CHTs here in Florida this summer. I run LOP at cruise. First order of business was replacing baffle seals as they were in bad shape. This reduced initial climb out temps by about 20F.

Next order of business was CHT at cruise running LOP. I was floating easily into 385-390F range 8,000’ OAT 56F with coolest cylinder around 365F. To combat this I was pulling power back to 56-60% to keep highest cylinder in the upper 370s. Not a terrible compromise in an RV as I was still doing 148KTAS, but a bandaid nonetheless.

After speaking with Trent at Emagair, I decided to re-time the mags for 2 degrees AFTER TDC. During the process I also replaced the old iridium spark plugs with 3961’s (per Emag manual) and replaced a few worn out spark plug terminals (be sure to ohm check the leads if you do this).

Timing the mags 2 degrees after TDC and replacing spark plugs contributed to the following results
- LOP cruise CHTs 8,000’ 53 degree OAT peak cylinder 366F at 67% power (I never run throttle firewalled at cruise)
- smoother and faster starting
- smoother idle and smooth shut down at idle cutoff

- very slight drop in performance
- increase of roughly .5 gal/hr at cruise

In my hot climate I am happy with this compromise for the results I seem to be getting.

 

[Dennis96080]

I'm firmly in Phase 1 testing having only about 10 hours on my -14A as of today. My cylinder head temperatures came down nicely within only 2-3 hours, and although my oil temps have also come down, that isn't saying much because they were at redline for the first few hours. Now they tend to hover around 220; far hotter than I would like, but at least not redline. Yes, I've checked my baffling and as far as I am able to determine it is perfect. I also don't have any obstructions to the oil cooler. I even tried taping off my heater inlet so as not to be "robbed" of a few square inches of inlet air (it made no difference). The only options I see left are to just keep flying since Lycoming says engine break-in can take 50 hours or more. My other thought is to try retarding the spark advance if the temps aren't down by around my first oil change. My home field is at 6200 feet, so I have been flying at pattern altitude for much of the break-in, around 7500 feet. That usually puts me at around ~23" manifold pressure and 2700 RPM. I'll occasionally dial it back to cruise RPM of 2450, just for some variation. Any other thoughts are welcome.

As for my flaps up stall speed, I'm having trouble nailing it down. When straight and level with the ball centered and the flaps up, it simply won't stall. It will buffet and establish a high sink rate, but it won't stall. I have to be at half or more flaps before it breaks and drops a wing. My empty weight is 1268 and I've tried testing at different all-up weights and with as much as 120 lbs in the baggage area. When the baggage area is empty, by CG is between 83" and 84". With 120 lbs in the baggage area the CG moves back to around 86"+. I can't put enough weight in the baggage area to reach the aft CG, so I'm normally going to be somewhere in the forward 1/3. As far as I can tell, the published flaps up stall speed looks about right. Anyone have a similar experience?

And just a few data points and some motivation for those still building, the pitot/static system is very accurate per my tests and calculations. Additionally, I installed the red cube per the plans and my fuel totalizer is also dead nuts on. No kidding. It wasn't even a tenth of a gallon off after burning 43 out of 50 gallons. I'm also seeing solid true airspeeds of 180-186 knots in level flight at full power settings (~13.3 gal/hr, ~23" and 2700 RPM). Very impressive!

My -14A also ran warmer than I cared for during Phase 1. Home field was also 6900'. I ran the -390 as hard as I could but did find oil temp dropped with RPM's below 2700. Cowl flap is only worth 8-10 degrees at best. Early data had CHT's running avg of 370 and oil temp was 195 with an OAT of 1C. As it broke in the oil temps have come down and the oil consumption dropped right at 50 hours. I also have poured over every loss of cooling air I can think of and ensured the timing is NOT advanced. It gets better.