Density altitude performance with a 1964 M20E

[Pilot boy]

Have a question.  First off, does anyone have any performance table from an E model with more in depth performance numbers?  The 1966 POH I use is very limited in the tables of performance information. I'm thinking maybe a 1970 C or E model POH might have more?  Anyone know how close those are for the older models?

Yesterday taking off from a 3,000 ft strip at 1,450 MSL but 95 degrees out and very humid I probably took off with only about 500 feet or less to spare.  Fortunately I took off in a direction with no obstacles (deliberately planned).  I was about 2450 lbs (100 under gross) with two large adults and about 40 gallons of fuel.  I checked the performance tables and they indicated I should have been off by about 1700 ft.  It seems it took more like 2500 ft as I said.  No automated weather but normally this temp around here would equal about a 4000 ft density altitude.  I realized afterwards that running full rich for take off was a mistake...the motor did seem a little weaker than normal.  I leaned for taxi but around here (flatland) normally I take off full rich.  I think I missed out on power because of it.  Just want to get people's take on how much you should lean for a very hot takeoff in the Midwest etc.  I did keep the plane on the ground longer than normal to make sure I hit 80 mph and I didn't want to float and lose speed by rotating too early.  I also had about a 6 knot tailwind as the runway was sloped downhill so I chose downhill over a headwind ...this also may have been an error, however the wind sock was flat at takeoff and the whole airport except the runway is surrounded by distant trees so the air was very still.  I am going to play around on a longer runway tomorrow to experiment with different mixture setting as I'm thinking I may have cost myself 100 or 200 RPMs due to being slightly flooded condition without realizing it.  Looking for thoughts or updated POH info.  Distance to clear a 50 ft obstace in at 2500 ft MSL and 100 degrees was 1855 ft at max gross of around 2550#  It definitely took me longer.

What's the shortest runway you'll use and with what weights/people and fuel etc?  I'm glad I chose to land at the 3000 ft runway instead of the 2000 ft runway the cessnas were using at the nearby airport.

[Scopes]

I suspect you’re going to get a lot of input here but my 2 cents (also having a 1964 E) is what you already know - high density altitude and high weights - for me the owners manual table is pretty accurate but I wonder how accurate your weight& balance calculation is. 2 large adults (say 220 lbs each) plus 40g fuel would put me at 2268 - you were almost 200 lbs heavier

in terms of shortest runway for takeoff, I think that is definitely based on your comfort and experience - my Mooney training was on a 3000’ runway,  I’m ok with 2000 for takeoff but would rather not land on one that short, but would definitely want to be spot-on with W&B

Edited August 24, 2020 by Scopes

[ShuRugal]

I don't have any Mooney-specific documentation, but I have seen a lot of information about mountain flying which states that when conducting high density altitude takeoffs, you should lean to peak RPM during run-up and use that setting for takeoff.

I'm sure someone more qualified than me will either back that up, or explain why it is wrong and what the correct action is.

[carusoam]

66 did not have a POH....

Don’t be surprised by the vocabulary used...

66 had an owners manual., which didn’t require the manufacturers to supply the important info you are seeking... (unless you are looking for the page that says how smart you are for selecting the worlds greatest aircraft) 

Get a POH from around 1977 for your bird...

Each year got more, and better information... but it never reached the level of completion that is in POHs today... it gives hints to operating outside of the perfect zones, but not real answers...

This document has gobs of data that you want...

You still need the OM from 66 to be legal for the ramp check...

 

POHs are available through your local MSC... I got mine by directly by calling Mooney back in y2k.... I spoke to some guy named Bill Wheat... that was his recommendation...  Bill has signed my first log book... right on the AW line... (that Bill Wheat)

 

Know what I mean?

Best regards,

-a-

[carusoam]

Pilot Boy,

Have you checked the download section for POHs?

I think you will find some interesting detail in there...

-a-

[Hank]

@Pilot boy, many POH / Owners Manuals are available in the download section here.

As someone above posted, I got my PPL, bought my C and was based for 7 years at a field 3000' long with trees at both ends--the preferred runway required leveling off on final at 150agl until past the trees, the other end had a displaced threshhold. Field was only 567 msl, but temps in the 90s were common. I don't recall a single takeoff, even loaded heavy for a getaway with my wife or a 4-person lunch run, that my takeoffs required even half of the field, and I was never worried about the trees at the end. Of course, when loaded heavy I did use Takeoff Flaps, but only when loaded heavy.

The shortest field I've flown my C into was a nearby 2000'grass strip. My limit there was half tanks and 2 people, so that I didn't have to worry about the gravel pile at the cement plant at the north end of the field. The big problem there was a hump that would throw you into the air at about 60mph, just as it bent to follow the river . . . Needed to stay close tomthe river bank for a smaller hump and shorter "flight"!

Your E should do similarly, as my 3-blade Hartzell should make up for the 20 extra hp that you have compared to me.

Then again, my first summer after moving back South, I thought my engine was about to need overhaul. Leaving a 5500-foot field at 777msl, I was less than 400 agl at the end of the concrete! Then I started paying attention to the DA part on AWOS. No worries any more!

[carusoam]

Having the POH data is the first part...

Making sure your plane’s performance matches the book... is the second part...
 

There are tools to confirm your plane’s performance...

• Eyeballs and landmarks on the ground...
• CloudAhoy and a WAAS source...

 

Don’t just expect the numbers in a 50year old book are going to work...

The cool part... with the app and WAAS resource, you can collect very accurate data about yourself, flying your own plane...

Take good notes in your travel log to include DA data... RH is also helpful...

 

Some People use a safety margin... to account for some shortcomings...

Unfortunately, there have been some people that haven’t accounted for all the details before departing...

 

Where things go off the rails... the math isn’t very linear... hot and heavy is way out on two edges of the data collection...

 

PP thoughts only, not a CFI...

Best regards,

-a-

[RLCarter]

This past Saturday I did a 500 nm flight that took me into an unfamiliar class G airport, 2500msl and 3500ft runway. DA was a big concern  due to being in a tired 172 which on its best day only had 145hp at a departure around 1:00pm in S. West Texas heat.. someone around here said their rule of thumb is the runway needs to be longer than the DA is high, I’ve played around with those numbers and like it. We’ve all done things that grab our attention and we need to use that to think things through and not as a “it worked out last time” . Personally I use a 50% margin over what the book says, which adds some wiggle room for not being “the best pilot ever”, old airplanes and what ever else tries get me 

[steingar]

Over the summer I did a landing at a 2200 foot strip on a 100 degree day.  I checked the book numbers and I could get in and out of there in those conditions even at gross.  It was just me and I made it in and out with no issue.

 

[takair]

I sometimes fly my E into an 1800ft, sea level, island airport at near gross...call it 100 under.  Density alt around there may reach 2500....Shown as 2000 as we speak.  I’ve never used more than half the runway.  There is a small bunker at the end that must be cleared or one must sidestep.  That can get a little close on a hot day, but I have plenty of water beyond.  I don’t lean in this situation.  You may get marginally more power in the situation you describe.

I feel like the bigger issue for you was a tailwind with relatively high DA.  That 6 kit tailwind will eat up a lot of runway on a hot day.  Technique becomes absolutely critical.  You will likely find that rotation to liftoff is a rather extended period of time. It is then easy to overrotate and the induced drag will make matters worse, so it is critical to pitch and hold ground effect for a few moments longer than comfortable until getting near Vx.....from there performance really improves rapidly.  Oh, and....this is where a takeoff with some flaps makes a difference.  Hard to say without knowing the airstrip, but I suspect the tailwind was worse than the slope in this case.  As you said yourself, good to practice this at a longer airstrip with artificial goals.  I would not do the 1800 ft runway if surrounded by trees, without headwind and if it was sloped severely.  In fact, there are 2000 and 3000 ft strips that scare me more than this particular 1800 foot runway.  
 

Might also compare some other performance numbers to see if you are making power.  What kind of cruise speeds are you getting and under what conditions and power settings?  A flat cam might run smooth but not put out power.  Good luck, stay safe and enjoy the plane.

Edit: I should emphasize, the airport I mentioned also has an alternate 2300 ft runway, so there are options when the wind does not cooperate with the 1800 footer.

[geoffb]

Leaning may have been a small factor, but you're not talking about a 7,000 ft DA.  I was just out of a rough 2,000 ft dirt strip at 3,600 MSL with a DA over 4,000 in a canyon with trees at both ends.  A little lighter than you, but not a whole lot and was well over 50 ft AGL by the end of the runway.  Practice your maximum performance takeoffs.  If you need to get out, takeoff flaps do help, get to full power right away, get the plane off the ground, get the gear up and hold 80 MPH.  You'll be amazed at what you can get in and out of.  Holding it on the ground to 80 cost you compared to getting the wheels off and into ground effect.  I'm not an ace, so if I can do it with a little practice, it's easily doable.

Oh, and watch Brian Painter's videos.

[Pilot boy]

23 hours ago, Scopes said:

I suspect you’re going to get a lot of input here but my 2 cents (also having a 1964 E) is what you already know - high density altitude and high weights - for me the owners manual table is pretty accurate but I wonder how accurate your weight& balance calculation is. 2 large adults (say 220 lbs each) plus 40g fuel would put me at 2268 - you were almost 200 lbs heavier

in terms of shortest runway for takeoff, I think that is definitely based on your comfort and experience - my Mooney training was on a 3000’ runway,  I’m ok with 2000 for takeoff but would rather not land on one that short, but would definitely want to be spot-on with W&B

I believe my weight and balance is fairly accurate.  I weigh 228, friend weighs 272, 240lbs for fuel, we probably had about 70 lbs of baggage and gear I added in.  I have it built out in foreflight from my w and balance from the flight manual when the avionics shop added new equipment.  It has me around 2379 lbs at takeoff.  I’m using exact arms for the seat notch I’m sitting in and I put his seat in an exact notch as well.  The only thing I can think of is maybe the flight manual weight and balance is inaccurate or my full rich with extreme humidity cost me some power.  It’s very hot the next few days here so I’m going to do some testing.

[Pilot boy]

22 hours ago, carusoam said:

Pilot Boy,

Have you checked the download section for POHs?

I think you will find some interesting detail in th

 

yes I have downloaded much data from thrrr it has been helpful.  They don’t have much for POH for my E though.  I have the manual they have listed.

[Pilot boy]

19 hours ago, Hank said:

@Pilot boy, many POH / Owners Manuals are available in the download section here.

As someone above posted, I got my PPL, bought my C and was based for 7 years at a field 3000' long with trees at both ends--the preferred runway required leveling off on final at 150agl until past the trees, the other end had a displaced threshhold. Field was only 567 msl, but temps in the 90s were common. I don't recall a single takeoff, even loaded heavy for a getaway with my wife or a 4-person lunch run, that my takeoffs required even half of the field, and I was never worried about the trees at the end. Of course, when loaded heavy I did use Takeoff Flaps, but only when loaded heavy.

The shortest field I've flown my C into was a nearby 2000'grass strip. My limit there was half tanks and 2 people, so that I didn't have to worry about the gravel pile at the cement plant at the north end of the field. The big problem there was a hump that would throw you into the air at about 60mph, just as it bent to follow the river . . . Needed to stay close tomthe river bank for a smaller hump and shorter "flight"!

Your E should do similarly, as my 3-blade Hartzell should make up for the 20 extra hp that you have compared to me.

Then again, my first summer after moving back South, I thought my engine was about to need overhaul. Leaving a 5500-foot field at 777msl, I was less than 400 agl at the end of the concrete! Then I started paying attention to the DA part on AWOS. No worries any more!

Hmm I did wait to rotate until about 80 mph indicated.  Still I’m sure it was over half the 3000 ft runway...I would guess looking back on it some more it was maybe 2300 ft or so.  Sloped downward w 6 knot tailwind that seemed a non issue but may have cost me some.  I read that every 2 knots tailwind can cost 10 percent increase in ground roll though with all tree# nearby I’m not sure how much of an issue that was.  It was very very hot (95) and it was very humid (probably 55 percent or so)1450 msl.  Still your C sounds like it did better 

[Pilot boy]

18 hours ago, carusoam said:

Having the POH data is the first part...

Making sure your plane’s performance matches the book... is the second part...
 

There are tools to confirm your plane’s performance...

• Eyeballs and landmarks on the ground...
• CloudAhoy and a WAAS source...

 

Don’t just expect the numbers in a 50year old book are going to work...

The cool part... with the app and WAAS resource, you can collect very accurate data about yourself, flying your own plane...

Take good notes in your travel log to include DA data... RH is also helpful...

 

Some People use a safety margin... to account for some shortcomings...

Unfortunately, there have been some people that haven’t accounted for all the details before departing...

 

Where things go off the rails... the math isn’t very linear... hot and heavy is way out on two edges of the data collection...

 

PP thoughts only, not a CFI...

Best regards,

-a-

I had foreflight sentry, my 430 waas, also on during the takeoff as well as the ads b transponder broadcasting.  Anyone know a way to find ground roll distance?  Foreflight log of the flight shows a lot but the sirport is so small I couldn’t see the normal overlay of the runway to see when I popped off the ground.  The data must be in there I just can’t get the level of detail ...

[Pilot boy]

8 hours ago, steingar said:

Over the summer I did a landing at a 2200 foot strip on a 100 degree day.  I checked the book numbers and I could get in and out of there in those conditions even at gross.  It was just me and I made it in and out with no issue.

 

What model do you have?  Full fuel solo or had you burned some off?  I’m sure if my 272 lbs buddy hadn’t been with me I’d probably have been off around 1700 ft, maybe less

[takair]

3 minutes ago, Pilot boy said:

I had foreflight sentry, my 430 waas, also on during the takeoff as well as the ads b transponder broadcasting.  Anyone know a way to find ground roll distance?  Foreflight log of the flight shows a lot but the sirport is so small I couldn’t see the normal overlay of the runway to see when I popped off the ground.  The data must be in there I just can’t get the level of detail ...

Did you use this track log page?

[Pilot boy]

4 hours ago, takair said:

I sometimes fly my E into an 1800ft, sea level, island airport at near gross...call it 100 under.  Density alt around there may reach 2500....Shown as 2000 as we speak.  I’ve never used more than half the runway.  There is a small bunker at the end that must be cleared or one must sidestep.  That can get a little close on a hot day, but I have plenty of water beyond.  I don’t lean in this situation.  You may get marginally more power in the situation you describe.

I feel like the bigger issue for you was a tailwind with relatively high DA.  That 6 kit tailwind will eat up a lot of runway on a hot day.  Technique becomes absolutely critical.  You will likely find that rotation to liftoff is a rather extended period of time. It is then easy to overrotate and the induced drag will make matters worse, so it is critical to pitch and hold ground effect for a few moments longer than comfortable until getting near Vx.....from there performance really improves rapidly.  Oh, and....this is where a takeoff with some flaps makes a difference.  Hard to say without knowing the airstrip, but I suspect the tailwind was worse than the slope in this case.  As you said yourself, good to practice this at a longer airstrip with artificial goals.  I would not do the 1800 ft runway if surrounded by trees, without headwind and if it was sloped severely.  In fact, there are 2000 and 3000 ft strips that scare me more than this particular 1800 foot runway.  
 

Might also compare some other performance numbers to see if you are making power.  What kind of cruise speeds are you getting and under what conditions and power settings?  A flat cam might run smooth but not put out power.  Good luck, stay safe and enjoy the plane.

Edit: I should emphasize, the airport I mentioned also has an alternate 2300 ft runway, so there are options when the wind does not cooperate with the 1800 footer.

I did use 2 pumps on the flaps for my takeoff flaps.  The slop was slight but almost the entire runway.  I think you may be right with the high DA of 4K feet then the tailwind may have played a bigger role than I thought.  I witnessed the Cessna using that direction but I probably should have gone the other way looking back.  My short field technique needed a lot of work.  My cruise numbers don’t seem great to me.  I’m doing this off memory but around 25 squared I’m probably seeing about 150 mph with a full load.  Probably 160 mph when by myself around 6500 to 7500 msl.  Do have the powerful exhaust but a 2 blade prop.

[Pilot boy]

Just now, takair said:

Did you use this track log page?

Yes this is what I was using but the airport is so small it doesn’t overlay a runway in foreflight so I can’t see the distance of the ground roll.  Can I change settings or pull the data somehow?

[takair]

18 minutes ago, Pilot boy said:

I did use 2 pumps on the flaps for my takeoff flaps.  The slop was slight but almost the entire runway.  I think you may be right with the high DA of 4K feet then the tailwind may have played a bigger role than I thought.  I witnessed the Cessna using that direction but I probably should have gone the other way looking back.  My short field technique needed a lot of work.  My cruise numbers don’t seem great to me.  I’m doing this off memory but around 25 squared I’m probably seeing about 150 mph with a full load.  Probably 160 mph when by myself around 6500 to 7500 msl.  Do have the powerful exhaust but a 2 blade prop.

Best convert the speed to TAS to get best comparison.  Those speeds may be  on the slow side, but TAS will vary and is a better indicator.....I really think the wind was a big player as was your rotation speed.  Sticking to the ground is not as efficient as getting airborne, gear up and Vx.  I think you will find that with practice you will do much better.  It is a continuous learning experience, and even when you think you have it down, give yourself an out....margin.  We all have bad days and margins erode quickly.

[takair]

25 minutes ago, Pilot boy said:

Yes this is what I was using but the airport is so small it doesn’t overlay a runway in foreflight so I can’t see the distance of the ground roll.  Can I change settings or pull the data somehow?

Just zoom with two fingers on the image...I think.  Which airport were you working from?

[Pilot boy]

3 minutes ago, takair said:

Best convert the speed to TAS to get best comparison.  Those speeds may be  on the slow side, but TAS will vary and is a better indicator.....I really think the wind was a big player as was your rotation speed.  Sticking to the ground is not as efficient as getting airborne, gear up and Vx.  I think you will find that with practice you will do much better.  It is a continuous learning experience, and even when you think you have it down, give yourself an out....margin.  We all have bad days and margins erode quickly.

I'm only about 25 hrs into the plane so I will try to refine my short field takeoff methods.  I plan to go tomorrow as the weather will be very similar to what it was Sunday with high temps but I'll be solo.

I'm glad I didn't use the 2000 ft runway at the nearby airport now.  Fortunately it was flat Iowa corn fields ahead of the runway if needed and just a slight rise in terrain.  I think I would have cleared trees by the end of the runway.  I cleaned up the gear very quickly once I rotated at 80 mph.  The Johnson bar makes that process fast once you get it down.

[Pilot boy]

6 minutes ago, takair said:

Just zoom with two fingers on the image...I think.  Which airport were you working from?

It was 0F3.  That's a zero.  Spirit Lake MN.  I tried to zoom or use two fingers to measure in the log page but it doesn't allow it like the normal map page.  Can you overlay the log into the map page somehow?

[takair]

6 minutes ago, Pilot boy said:

It was 0F3.  That's a zero.  Spirit Lake MN.  I tried to zoom or use two fingers to measure in the log page but it doesn't allow it like the normal map page.  Can you overlay the log into the map page somehow?

You can export to Google maps and might get a sense of what happened. It will even do 3D view, which is cool.  I also think that cloudahoy (something like that) will work.  Hit the “send” arrow for some options on exporting.

[Hank]

80 mph sounds mighty fast to rotate. Check your Owners Manual for a page like this one from my C:

I generally pull baxk at 70mph; heavy I'll go to 75; with crosswind I may add the gust factor then yank off the ground. But I've never increased rotation speed for DA. I've also never taken off with a noticeable tailwind, and hope to not land with another one anytime soon.