M20C Foreflight flight plan performance numbers

[MCDsiena]

What is everyone using for performance numbers in Foreflight for a stock 66' M20C?  

Taxi/Takeoff fuel use?

Climb TAS?

Climb GPH?

Climb Rate?

Rinse and repeat for descent?

I've been using 135knots at 10GPH for cruise, although in the new to me airplane without any long cross countries with a lot of take offs and landings I have not accurately verified that data yet. 

Thanks

 

[Raptor05121]

Start/Taxi/Takeoff: 1 gallon (small county airport, no tower, hangars only 1/4 mile from the end of the runway)

Climb 120mph @ 18gph

10gph is good for planning purposes, it'll leave a few gallons in the tank if you're only burning 8.5-9.5/hr. Others with more time than me can adjust as needed.
 

[Hector]

Start/Taxi/takeoff : 1.5 (towered field)

Climb at 105 Kts/500fpm/15 GPH (with everything to the wall I burn 17.5 but over a long climb to 7.5-10k it averages to 14-15 GPH or a little less)

Cruise: 135 Kts/9.2 GPH (typically between 8.7 and 9.2 at 22 inches and 2400 RPM which is my typical cruise setting. This is conservative since my C actually does 140 Kts consistently).

Descent : 150 Kts/500 rpm/7.5 GPH

These are the numbers I use in Foreflight

[StinkBug]

I'm pretty close to Hector. I flight plan at 135kts and I'm usually close or a little faster. In the online flight planners I put in 14GPH for the climb at 100kts, 9 for cruise at 135, and descent at 8gph/150kts. I fly at 23/2300 and over most of my long distance flights this has put me within a gallon or so.

This weekend I flew from San Diego to San Francisco. Fuel is cheaper up there so I only put in what the planner calculated, plus 10 gallons. When I landed I had 11 on board. I try to never land with less than 10, but will aim for as close to that as possible if I'm going somewhere with cheap fuel. Those numbers seem to work well for me. 68C, totally stock except the Hartzell Scimitar prop.

[bonal]

Interesting question and I'll be honest I don't calc fuel in climb and descent a very typical profile would be an 8100ft climb from home 1400 elevation with a long descent if terrain permits and I always average out between 9 and 9.5 total per hour. I flight plan at 140 knots average for the flight even though my climb is 120mph and always hit my planned 140 knot average. Ground speed will always depend on winds. I plan a max 3 hour leg and cruise at 2450rpm MP above 7500 feet is rarely better than 21 inches. Most I've ever been able to put in after 3 hours is 28 gallons. In summary it's a very consistent 140knot combined average speed.

like Hank I don't pull power for the descent and often see speed just below redline when the air is smooth.

[Hank]

I plan on 140 knots +/- winds aloft, and 9 gph. I climb at Vy, with an eye on Oil Temp this time of year. Cruise is generally 23/2300 down low, 22/2400 for mid-level flights (an hour or a little longer), and WOT less a hair /2500 when nice and high. I sometimes remember and lean to my Target EGT.

For descents, I push for 500 fpm and trim. Every now and then I'll pull throttle back to cruise MP, and push mixture forward to cruise EGT. This generally has me coming down around 170 mphi; I've seen ground speeds range as high as 203 mph on my cell phone GPS, it's very common to be 160+ knots on the Garmin.

My longest leg so far is 4:40, and I put in 41 gallons. Right now, I'm too tired to do the math . . . But no, I don't have fuel flow, just a calibrated dipstick and a yoke clock with settable, non-moving red hands; whenever the white minute hand is over the red one, I flip the fuel switch on the floor.

Speed mods:  guppy mouth closure, 201 windshield, and a 3-bladed air brake. I figure they cancel each other out on everything but climb speed.

Happy flying!

[MCDsiena]

Thanks guys, this gives me a great place to start. I've got a new to me M20C and so far have just stayed in the pattern working on landings. Once I get my insurance requirements in and start planning some longer flights I'll fine tune he numbers. 

[Hank]

Go to other airports as part of your training! I visited most within ~50 nm, and several further away, just trying to get the hours burned off, learn the plane and get comfortable in it. It's considerably different in flying characteristics than the Cessna I learned in . . .

[MCDsiena]

You can say that again, I am a new 60 hour pilot with all 60 of those hours in a 152.  I've been driving two hours one way to fly with the man I purchased the plane from (he owns 4 Mooneys among other planes with thousands of hours) to get some unofficial time in the plane with him flying, just to get a feel for sight picture, landing attitude, and general flight characteristics. He is delivering my plane to my home airport hopefully this coming week then I can get with my CFI to knock off the complex rating and the required insurance hours all while getting the proper transition training. Then I will be able to spread my wings a bit. 

[Hank]

Congrats, MC! I had 62 hours in 172s when I bought my C, right at my home field. Just had to knock out the rating and insurance dual. We went lots of places after I showed that I could fly the plane and actually land on our 3000' field. At the time, I thought 4000-5000 msl was pretty high, but we trained a lot at 5500 and up. Now I routinely fly 7500 and up when I travel.

Congratulations in a great choice! Learn the V speeds, get to where you can set up 90mph with Takeoff flaps on downwind quickly and easily. Then you can concentrate on everything else--maneuvers, climbs, power in descents, and that strange thing to Cessna pilots--setting cruise power and leaning the engine.

Have fun, and fly safe!

[Nukemzzz]

I’m new to this and I’m confused by this topic and how it is used in ForeFlight. Everyone is reporting one number (Knots) for cruise and I think they are referring to the gage reading when OP needs TAS.  The Mooney POH displays TAS vs altitude on a standard day, and ForeFlight doesn’t give a reference altitude so I don’t know which to pick. . I’ve searched the whole internet on this topic and there seems to be a lot of confusion. 
 

For cruise in the M20e in foreflight  I’m using 165 knots TAS @ 10.8gph at 2500/23 which I pulled from the 7,500 ft performance chart since I think I’ll usually be around that altitude when on cross country and I’m at full throttle because I don’t see the point of going slower to reduce gph only to be in the air longer and end up burning nearly the same amount of fuel to the destination while losing my time and engine time but this part is a personal preference clearly.  
 

Am I doing this wrong?  What number is foreflight looking for here?  It’s asking for a number that depends on the environmental conditions and altitude and so it doesn’t add up. Are they just trying to sell me the performance plan that does adjust for altitude?
 

 

[carusoam]

Nuke...

Are you putting too much thought into what other people are doing?

What is right for you? Your machine?

Chances are... book numbers aren’t very accurate.

Collect your data the best you can and enter it into your flight plan...

Then fly your flight plan...

What if your flight plan changes?

How critical are these numbers?

Who is using them while you are flying?

In the end... distance travelled over the ground and fuel used is where the accuracy counts...  

You need to complete the trip, with a positive number of gallons in the tank....

It helps to have a GPS and a FF/fuel totalizer instrument too...

PP thoughts only, not a CFI...

Best regards,

-a-

[smwash02]

Nuke,

You're overthinking something that isn't able to provide an exact answer but rather a close estimate.

With my C I flew between 7 and 10 in most cases and the numbers aren't hugely different. I set the GPH a little high and TAS a little low since winds are anyone's guess really over a distance (affects GS) and I usually came out close. People's numbers numbers above are close to what I used in my 66C. This is what the simple version is designed for.

The C and E POH are usually in MPH (depends on year). 175 KTAS is not realistic for a E but 175 MPH sounds close.

[Nukemzzz]

See the attached picture of the foreflight performance section for a trip I’m planning. My question is: why foreflight isn’t specifying an altitude when asking for TAS. This performance section is independent of any trip. It’s a “profile” of the plane. For now I‘ve entered values from the 7’500 MSL table for 2500/23. 
 

I fully understand that these are estimates. However, it’s bad practice to start off entering numbers that don’t seem to be right. 

[Nukemzzz]

16 hours ago, smwash02 said:

The C and E POH are usually in MPH (depends on year). 175 KTAS is not realistic for a E but 175 MPH sounds close.

Thanks for the reply.
 

The POH says 183-187 mph which I’ve converted to knots. The reason 165knots (and 187mph) sounds high is because this is TAS at 7,500 MSL. Indicated airspeed will be 15% less than actual at 7,500 ft on a standard day if I understand things correctly.  This means the gage will read 143knots when TAS is 183-187mph.

Foreflight is asking for TAS and not IAS but doesn’t mention altitude.  Confused...

Edited December 25, 2019 by Nukemzzz

[Nukemzzz]

It seems to me that foreflight should be asking for desired IAS in these profiles, and then based on the chosen altitude and atmosphere conditions for the trip, calculate TAS for the trip. Things seem backwards in the app to me. Of course I could just be confused. That’s why I’m asking. 

[carusoam]

Nuke,

some short notes on TAS....

https://en.wikipedia.org/wiki/True_airspeed

For people with a fancy ASI, they can enter the OAT in one window, and read the TAS using the other window...

The TAS is temperature dependent... I don’t see a place to enter the altitude...

 

So...

1) following a tradition makes some sense...

2) It may help ATC with their separation responsibility... sort of...

3) In the end it is highly weather dependent, altitude dependent, throttle position dependent...

4) Lots of variables that change on the fly...

 

PP thoughts only, not a CFI...

Best regards,

 -a-

[Nukemzzz]

I ended up taking the trip shown in foreflight on monday when I brought the Mooney home.  It took 4.5hrs instead of 3.  Strong crosswind caused me to crab most of the way home.  3/4 was at 9,500 at full throttle, power boost on, 2500 RPM.  Then changed to 24 squared after the engine started running rough (turned out to be a blown muffler).  Either way, IAS was about 143mph at 9,500 at those settings and this is nowhere near the 143knots IAS that I expected.  I thought the gage was going to be running in the yellow at cruise (+150mph).  What I'm learning is the environmental conditions of the flight are such a big factor that pre-flight calculations are just very rough estimates to see if you might have enough fuel.  However, it does seem like the POH is very optimistic of the plane capability...at least when it is 64yrs old.

[Ragsf15e]

48 minutes ago, Nukemzzz said:

I ended up taking the trip shown in foreflight on monday when I brought the Mooney home.  It took 4.5hrs instead of 3.  Strong crosswind caused me to crab most of the way home.  3/4 was at 9,500 at full throttle, power boost on, 2500 RPM.  Then changed to 24 squared after the engine started running rough (turned out to be a blown muffler).  Either way, IAS was about 143mph at 9,500 at those settings and this is nowhere near the 143knots IAS that I expected.  I thought the gage was going to be running in the yellow at cruise (+150mph).  What I'm learning is the environmental conditions of the flight are such a big factor that pre-flight calculations are just very rough estimates to see if you might have enough fuel.  However, it does seem like the POH is very optimistic of the plane capability...at least when it is 64yrs old.

The Mooney charts are notoriously optimistic for cruise.  If you have a good clean E, you might see just over 150kts TAS in cruise.  More likely, plan for 148 kts TAS at 10gph.  That will be a starting point and you can adjust from there.  The adjustment won’t be much.

Right now your foreflight profile from above actually has you slowing in the descent... lots of techniques on this, but no reason if you actually want to go fast.  Leave cruise power, trim down for 500fpm descent.  Only pull power if required to remain below Vne or enter the pattern (no turbulence).  Foreflight descent should be something like 170kts, 10gph.

 I fully understand someone with an E is going to swear they get 180kts on 8gph, but start close to my numbers above and make very slight adjustments.  You’ll be in good shape.

[smwash02]

The POH is a little optimistic, but there is a bigger disconnect in your understanding of IAS and TAS.

Looking at the POH for a 66E at 10,000 full power and 2500 RPM and 2575 pounds a beautifully rigged properly trimmed with perfectly indicating gauges plane will show 181MPH TAS. That's TRUE airspeed, not INDICATED airspeed.

How do we figure that out? Properly done we need the temperature, barometer setting, etc. Roughly done add 2% per 1000 feet to your IAS and you get TAS. In the above example 153MPH IAS == 181MPH TAS using the 2% fudge method.

In your case showing 143 MPH is 169MPH TAS -- about 11mph shy of the book, frankly, not bad since you have so many factors to potentially gain it back -- properly leaning,  checking airspeed indicator, checking tech accuracy, rigging, perfect trimming, draggy antennas, fully closing gear doors, cowl flaps, cleaning and waxing,  list goes on.

As I said above, 175MPH TAS is what I think is realistic. Where did you get 143KIAS (165MPH) indicated expectation from?

[Nukemzzz]

16 hours ago, smwash02 said:

The POH is a little optimistic, but there is a bigger disconnect in your understanding of IAS and TAS.

Looking at the POH for a 66E at 10,000 full power and 2500 RPM and 2575 pounds a beautifully rigged properly trimmed with perfectly indicating gauges plane will show 181MPH TAS. That's TRUE airspeed, not INDICATED airspeed.

How do we figure that out? Properly done we need the temperature, barometer setting, etc. Roughly done add 2% per 1000 feet to your IAS and you get TAS. In the above example 153MPH IAS == 181MPH TAS using the 2% fudge method.

In your case showing 143 MPH is 169MPH TAS -- about 11mph shy of the book, frankly, not bad since you have so many factors to potentially gain it back -- properly leaning,  checking airspeed indicator, checking tech accuracy, rigging, perfect trimming, draggy antennas, fully closing gear doors, cowl flaps, cleaning and waxing,  list goes on.

As I said above, 175MPH TAS is what I think is realistic. Where did you get 143KIAS (165MPH) indicated expectation from?

Thanks for the reply. I don’t think I misunderstand TAS vs indicated. But this is why I’m asking. I’m a student by the way and this is why I’m in the POH and overthinking things. 
 

Prior to the trip I planned to run about 7,500 MSL. I pulled 185 TAS from the attached table. 2% per 1000 ft is 15% at 7,500. So 185/1.15 = 161 mph (for some reason my result is slightly different this time. Maybe used 2600RPM). Either way I assumed that to be indicated and what I saw was just over 140MPH indicated. 

If I do the same thing at 10,000ft, closer to actual, I get 152MPH indicated.  This is pretty close considering this is an old bird with original paint, seals, imperfect surfaces, and I haven’t been able to wax it.  Also, Mooney tested in perfect conditions with Chuck Yeager on the yoke I’m sure. 

Oh well. Close enough. Turns out the winds and clouds make all of this a moot point anyway and this is what really killed my trip time. Lmao

[smwash02]

The POH is always the best place to start, but sounds like you've got a firm grasp of it all.

With my C I used 140kts to estimate my flights and it was always reasonably close unless winds were strong (Usually saw 145-150KTAS). In the E I would expect you to be able to plan for a bit more.

Best of luck on your training!

[kortopates]

Foreflight doesn't do precise performance modeling like you seek. If you are OCD about that like Iam, then could you use Garmin Pilot like I do or for free use flightPlan.com which also does that.
But with a Normally aspirated engine you'll find it makes little difference since you only fly a just a couple practical altitudes. It really doesn't make much difference till you're flying a turbo that goes faster and faster with altitude and flies any any altitude up and into the flight levels.

But all apps that do model performance fully all want TAS for a given density altitude and fuel flow, and they also allow multiple entries for different % power. So you could create tables for 75%, 65%, 55% power. Nobody wants to put in IAS, since TAS represents the actual performance you expect. Accurate numbers for TAS and FF at density altitude and the apps ability to use pretty accurate forecasted winds aloft results in very close to actual times and fuel burned.


Sent from my iPhone using Tapatalk

Edited January 2, 2020 by kortopates

[Ragsf15e]

3 hours ago, Nukemzzz said:

Thanks for the reply. I don’t think I misunderstand TAS vs indicated. But this is why I’m asking. I’m a student by the way and this is why I’m in the POH and overthinking things. 
 

Prior to the trip I planned to run about 7,500 MSL. I pulled 185 TAS from the attached table. 2% per 1000 ft is 15% at 7,500. So 185/1.15 = 161 mph (for some reason my result is slightly different this time. Maybe used 2600RPM). Either way I assumed that to be indicated and what I saw was just over 140MPH indicated. 

If I do the same thing at 10,000ft, closer to actual, I get 152MPH indicated.  This is pretty close considering this is an old bird with original paint, seals, imperfect surfaces, and I haven’t been able to wax it.  Also, Mooney tested in perfect conditions with Chuck Yeager on the yoke I’m sure. 

Oh well. Close enough. Turns out the winds and clouds make all of this a moot point anyway and this is what really killed my trip time. Lmao

We’re all kind of telling you the same/similar thing, but potentially not clearly...  be careful with multiple conversions - mph to knots and TAS to IAS.  In fact,  IAS may be nice to know, but it’s almost irrelevant in cruise.  You need your TAS to make sure you’re meeting performance (engine, drag, etc).  You need your Ground Speed to make sure your fuel plan is working.

Foreflight is generally set up for knots and it doesn’t care about ias.  You input true airspeed in knots (although I think you can set it for mph).  Most aviation is knots so I’d recommend that even though your poh is in mph like mine.

If you plan a flight, ForeFlight will then use forecast winds at your planned altitude to compute ground speed.   

Build a basic ForeFlight profile for a few altitudes and rich/lean of peak.  Say 5,500, 8,500, and 11,500.  That’s 6 performance profiles right there.  Use the profile closest to your planned cruise numbers - ie if I plan to cruise at max power at 10,500, I’ll use my 11,500 rich of peak profile. 

If you start with a cruise profile ~7,500, 150 kts (true), 10gph you’re gonna be really close for most normal cruise settings.

[carusoam]

Nuke,

Take notes each time you fly... on all the things like weight and balance...

I see the POH covers weight in the performance chart... but balance will add or subtract a few mph as well...

As you collect data... it helps to remember what it is like to fly near MGTW and when near empty...

If you fly around with bags of sand... make them wear seatbelts...  

PP thoughts only, not a CFI...

Best regards,

-a-