Reduced Power to Increase Range in Vintage Mooney?

[Piloto]

Sean

 

I fly the KFXE-TJMZ or TJIG route twice a year. I always encounter some headwindos about 10 to 15 kts. I go non-stop to avoid refueling and Customs that can easily add 2 hours to the trip. My plane has long range tanks that makes it easier for the 900nm trip. I hear from others that Providenciales MBPV is a popular refueling stop. It may not be worth going slow because the headwinds will limit your range anyway.

 

José   

[Oscar Avalle]

Thanks Oscar. That is actually not a bad price and the extra fuel buys a lot more piece of mind. Just curious, where is the fuel in the ferry tank pumped into the mains?

 

 

Here are some pictures on how I connected the ferry tank to the fuel tank. I got a ferry permit.

[garytex]

I haven't spent more than a couple hours there, but I can hit that 23 to 24 statute MPG that johnathanpaul got in his E pretty easily in my F which has SWTA mods. 2075 rpm, 21" 8500, 78 df, (and the high DA may have been the trick there) 6.2 gph  very slightly (10 degrees mas o menos) LOP and 145 statute mph true.   Even if the mods were good for 10mph (which I doubt) a straight plane at 135 mph would be good for 22 mpg.  I bet anybody can do it.

I had the dogs in the plane and was looking for a quiet cruise to save their ears. The plane had a disquieting vibration there, engine balance related I think, and I didn't like it. But it was quiet, and really efficient.  

I usually run 2450, in the high seven gph range when it is warm to the low eights when it is cool, 50 lop, 165 to 170 statute true. That last 20 to 25 mph comes at 10 to 13 mpg for each extra gallon burned but I am willing to trade for the smoother engine and extra speed.

Checking mileage in flight is a handy reminder, and unless I am in a hurry (and yes, I know 5 mph makes absolutely no difference in time over my usual 200 mile mission) if my mileage isn't better than 20 statute mpg that's my reminder to start working the knobs.  Low 9ish gph is usually peak for me, and gets me another 5 to 7 mph, a bad trade in my book, and tenish is only good for another 2 or 3 mph, an exceptionally bad trade.

The stinker just won't go much faster than 178 mph, no matter how much fuel I throw at her. It seems strange to me.

It also just blows me away that our planes were flown like that for thousands of hours earlier in their lives.  Mind boggling.  Thousands of gallons of fuel, and a couple hundred miles of range on every trip, just turned into mostly noise.

And while I'm waxing philosophical, have you ever seen a combination THat approaches an IO 360 and a Mooney airframe for turning gasoline into speed and distance as well as what we've got?  Surely not in the certified world. We are lucky to have them.

[DS1980]

X2 on the Carson's speed suggestion. Kudos Mark.

 

Sean- Carson speed will be 1.316 x V _L/D  As you can see, it is based on the best glide speed of the aircraft, so it is the same formula for any aircraft. It will be the best baseline to start with.

 

It seems you will need some sort of long range tank, if for any other reason to give yourself time to sort out problems. Especially for your first time.

[201er]

Seems to be like the fuel savings improvement is substantial going from 2700 to 2400RPM and anywhere in between. Going below 2400RPM provides greatly diminishing returns. Lose a lot of speed, gain a little fuel economy.

 

In theory you want to set your MP with altitude, not throttle. If you gotta pull the throttle, you're wasting potential. Go higher is winds negligible. However, the issue is cooling and LOP ops. Seems that once you get over about 8 or 10,000ft, you no longer have sufficient MP to run LOP. IAS is low so in CHTs go up. This forces you to go ROP but then you lose fuel economy. Going ROP at 13k ends up being the same or possibly less efficient than going 8k LOP in NA IO360.

[Z W]

He doesn't have an IO-360 in his G model.  He has the O-360, carb'd.  LOP isn't an option.  It is more efficient, though, to fly high (9-12k) and lean to peak EGT with the O-360.  You'll get a higher TAS for the same MP and fuel flow.  That helps, unless the headwind is stronger up high.

[Piloto]

Here are some pictures on how I connected the ferry tank to the fuel tank. I got a ferry permit.

That is quite an arrangement. The three occasions that I needed extra fuel I used a steel 55 gallond drum connected to the right tank fuel pick up line using a fuel selector valve. The selector valve either selected the ferry or the wing tank. You take off on the left main and then select the ferry tank. You want to empty the ferry tank first to insure no problems with it. After you empty the ferry tank you go on the mains. This set up does not requires a portable fuel pump so is very reliable. You do not need to empty the wing tank to see if the ferry tank works 

 

One thing to be careful about refueling wing tanks like on your set up is the posibility of overfilling, thus dumping fuel thru the tank vent without you knowing. Do not rely on the fuel gauges but look for any fuel contrail behind the wing.

 

Unlike the Turtlepac when I get to the ferry destination I just dump the tank, don't need to carry it back.

 

José 

[DS1980]

He doesn't have an IO-360 in his G model.  He has the O-360, carb'd.  LOP isn't an option.

We don't know this yet. Some carb engines run just fine LOP with the aid of carb heat and throttle adjustment.

[garytex]

DS1980 I agree. Tiny little tweaks of the throttle can do the trick.  Peak on a carb motor up high is also a good trick.

[Hank]

No success yet in my C. The next try will lean at WOT, then reduce throttle in search of smooth; back to WOT, add some carb heat and repeat. In the past, I've always reduced throttle first. Recent discussion in another thread suggested using this different order. YMMV, don't end up UWOF, etc.

My few attempts running the endurance settings (20"/1950?), I didn't like the mushy control feel. It's so easy to run at lower speed at 2300 and set MP wherever yields the desired speed (as for not running over a C172).

Backing off from 50 Rich to Peak cost 5-8 mph at 9000 msl, but I have no fuel flow. Thirty minutes of each still burned 9 gallons on my stick.

[DS1980]

Hank keep trying. Seems like you just need to find that one setting that smooths it out. As far as getting back to the topic, I would suggest trying LOP. It would add that much more buffer room for a long distance run. If you would like tips on how to go about it, just shoot me or Byron (jetdriven) a message. There are others on this forum that are experienced with it as well, Just verify advise that is given to you. Don't give up if at first it doesn't work. As Hank is finding out, a carb engine takes some fiddling to find that one setting that allows LOP. Running LOP at some function of Carson Speed just might get you close to where you want to be. Although it may be too slow for your liking.

[jetdriven]

He doesn't have an IO-360 in his G model.  He has the O-360, carb'd.  LOP isn't an option.  It is more efficient, though, to fly high (9-12k) and lean to peak EGT with the O-360.  You'll get a higher TAS for the same MP and fuel flow.  That helps, unless the headwind is stronger up high.

 

Higher to take advantage of tailwinds going East, and lower, down to 1000' AGL going west and low MP to get maximum range going West.

 

I read somewhere that maximum range is independent of altitude, which means that you should use altitude solely to play the winds.

 

I have also determined that running 55% or less power, peak EGT is pretty much the most efficient power setting for NMPG. Approaching 35-40% power, a few degrees ROP seems to work best.  The airplane falls down behind the power curve and spends a large portion of its time recovering the speed if LOP. You can see this in holding. The airplane at 3.8 GPH loses 5 knots in the turns on the hold, and spends the entire minute of level flight recovering that, if it can.  Its below L/D_MAX If it can't, the next turn in the hold causes it to get really slow. Then you add power, and screw it all up.

[DS1980]

Byron- range is independent of altitude? Does that sound right to you? It seems that the reduction in induced and parasitic drag would outweigh the loss in horsepower. Do you have the article? It just doesn't sound right, although it may be. I just might learn something today.

[jetdriven]

Check the POH, 36% power range is ~1220 NM, and this is at all altitudes sea level to 10K feet, but you have to use fuel to climb to 10K feet, so in effect, 36% power range is the same at all altitudes.  interesting reading.

 

you have pumping losses from less than  WOT at low altitudes, and you burn more fuel to climb to higher altitudes. Note the higher range values are at 2000 RPM, which is a more efficient prop setting.  The engine is less efficient from a BSFC standpoint, but the prop at low RPM is more efficient. The airframe has the minimum drag at the 113 KTAS (sea level) to 138 knot (10k feet) TAS airspeed a a weight of 2300 lbs. This likely correlates to the same AOA, the same % power,  and the same IAS for all altitudes.

 

Also, to further qualify this, it applies to non-turbo piston airplanes. The turbos may go father the higher you go, I am not sure one way or the other.

N201DA POH.pdf

[jetdriven]

del

[DS1980]

Wow. Demons exercised. I would have never thought that. Thanks for the input.

[201er]

I would think that on longer distance flights, the power used to climb is more likely to pay off with better TAS aloft.

[DS1980]

I would think that on longer distance flights, the power used to climb is more likely to pay off with better TAS aloft.

Apparently this is only true with a tailwind. I believe it, it's just hard to believe. Makes me wonder how many pilots know this, since this is not what I was taught.

[DS1980]

Now that I'm really looking at Byron's POH:

 

Lets go with 2400 RPM since that is available for all altitudes, and max MP for that setting. 2300 pounds, best economy cruise range at sea level is 827 and at 14,000 feet is 1068. So there is more range up high.

 

But looking at the Time, Fuel, and Distance to Climb chart: Obviously no fuel to get to sea level. Going to 14,000 at 2300 pounds, 23 pounds of fuel. This assumes Vy, which we don't do in Mooneys, so it would be a less efficient climb.

 

But the intro to the Range Tables is: "All Cruise and Range Data tables allow for: warmup, taxi, take-off, climb at max. power at the best rate of climb speed (Vy) to cruise altitude."

 

As stated, we don't climb at Vy, but would this make that much difference?

[Hank]

Why do "we" not climb at Vy? I do, temperatures permitting. The factory recommends it, Bob Kromer recommends it, and as you say, it's more efficient. It works well for MY Mooney.

[DS1980]

Hank,

Well said. In my experience, climbing at Vy in a slick airframe with poor cooling (stock engine inlet anyway, C-E models) didn't seem in the spirit of the airplane, and it only got me high CHTs. I started flying Mooneys in Vegas and I could only fly at Vy for a short period. Then to cruise-climb I went.

 

If you can do it, go for it. You hit it on the head in that you do what is right for you, as there are many correct ways to fly an airplane in any phase of flight. But overall, flying with other Mooniacs, I don't think that "we" do that. Besides, don't you have some LOP testing to do?

 

This still doesn't answer why there is more range at altitude.

[DonMuncy]

It is an absolute certainty, you get more speed with less fuel at altitude. The only question is whether you will gain enough more there to offset the extra fuel it takes to get to that altitude. Intuitively, it would seem to me it should hinge on how long you stay up there. But I don't claim to have any data or authority for that belief.

[Hector]

It would be more efficient for you to climb at max range speed, Hank, which in your C model is 101 KIAS. You'll obviously get better engine cooling there, too, than at Vy. Jim

Max range and max glide both occur at max(L/D) which according to the POH for my 67 C is 105 MPH indicated. In order to maintain all temps at or below 380 in the summer I have to climb at 120 MPH. Sent from my iPad using Tapatalk HD

[Hector]

No worries Jim, the original poster flies a G model so I wanted him to know his numbers may be a little different than a J. Sent from my iPad using Tapatalk HD

[DS1980]

I think for the short bodies, there are 2 best glide speeds. One for prop windmilling and one for prop stopped. One is 100 and the other 105.