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Posted

I'd like to get some input from any list members who have taken their M20C up to 11-15k for longer cross countries in order to determine what TAS I could expect.

Thanks in advance for your help.

Mitch Berger

M20C N6503U

Posted

TAS doesn't change much with altitude in a non-turbo Mooney.  As you climb, MAP drops, so there's not much change in performance.

The 'C' seems to be happiest at 6-8K in a no-wind situation.

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Posted

I've flown my "C" at 12,000 a couple of times.   Not for better TAS but to clear the rocks. 

TAS as Mooneymite says remains about the same, or falls off a bit as you get above 8000.  I saw about 140 KTAS at 12,000 but the fuel flow is lower than at 8000 as you see only 19-20" of MP up there.  

Posted

I did 650 nm and all of it between 12,500 and 16,500 in my C a couple of weeks ago.  I was getting between 150 and 155 knots TAS. But that's pretty much what I get all the time.

  • Like 1
Posted
 

I did 650 nm and all of it between 12,500 and 16,500 in my C a couple of weeks ago.  I was getting between 150 and 155 knots TAS. But that's pretty much what I get all the time.

Wow I would have never thought this, tables seem to predict otherwise.   I've never taken my C above 9500, and did seem to take a performance hit there over 7500 where it seems happiest.  Can't wait to try it out one day with an instrument rating and some O2 on board.

Posted

11.5 k' and 12.5 k' on the return in a fully loaded C were the norm for my family.  The NJ to MA run with a family of four.  The altitude selected was a gliding distance decision.

Climb rate at 120 mphias was good enough to get above NYC airspace before going too far out to sea.  120 was good at keeping the single CHT indicator coolish.

Wish I had MS back then.  JPI and FF didn't become widely available or nearly affordable until years later.

Since it was the norm back then. Grab an oximeter and give it a try.  Get used to using the oximeter a few times on a few flights.  Don't expect oxygen to be a problem at these levels. Just know that decision making can get more challenging as your O2 saturation drops.

Bring the Fitbit along for continuous heart rate monitoring while you are at it.

Best regards,

-a-

Posted

 Unfortunately that memory was lost years ago.  The way I looked at it was the GPS derived ground speed for the NA engine didn't make enough of a difference to plan the flight any differently.  Balancing power made, with air resistance endured, the altitude around 7.5k' should be best.  Throw in some variables like temperature and air density it is a fun experiment.  Clean and smooth all the surfaces and close all the gaps to see how fast your individual machine can go.

The objective of my trip was to traverse a 200 NM distance as quickly as possible.  The C does it quickly and on a low budget compared to the O.  O, less than 1.5 hours, C more than 1.5 hours.  Headwinds would take longer than 2hrs with the C.  Use less weight, less antennae and optimism your WnB to see some gains.

Keep track of the MP as you climb FT.  There may be some disappointment with that compared to the MP you get in the winter on the T/O roll...

I wish I could get those memories back. :)

-a-

Posted

I often fly longer XCs at 9000 or 10,000 (or 9500/10,500 if VFR). Going above that the climb rate gets pretty slow. I did cruise over the Carolinas and WV at 11,000 coming home from Sun n Fun since the winds were pretty strong out of the west; still caught some gentle mountain wave, riding up and down 300-400 feet. I'm attaching a typical panel shot, half at a time.

image.jpg

image.jpg

  • Like 1
Posted

I routinely operate a 68C in the low to mid teens in the intermountain west.   Fortunately I have the luxury of waiting for bluebird days at this stage of my aviation career for most ops.  We crossed the Sierras over Yosemite NP this past November at 16k, the highest I have taken this aircraft, just because we could. 

It is not unusual to see 145+ ktas (according to the genie that lives in the GNS430W) as the fuel load burns off.  Most of my trips are one or two up with minimal baggage and I am a firm believer in a pulse oximeter and supplemental O2.

Dollar for dollar it is hard to beat a clean and properly rigged C for this sort of mission.

All the best to all of you for 2016.

 

 

Posted

I'm in an F, so a bit different, but I routinely fly above 10k out west.  Oxygen is a good idea, pulse ox is also a good idea... I like it up there, but I definitely notice a slowing TAS above about 9k.  Usually the gallons per mile get better as long as you don't mind going slower.  When I say "slowing", I'm talking about a couple knots - maybe 3 or 4 at most.  The wind and its effect on your GS will be a much bigger consideration than any change in TAS.

  • Like 1
Posted (edited)

I fly a stock 'C' and I try to load the plane to give me an aft CG.  90% of the time I cruise at 9,10, or 11K.  At 9K I usually see 141-142ktas.  At 11K I see 140ktas,  I have flown it at 15K twice and saw 135ktas and 137ktas.  So speed does drop off a little.  Like Ragsf15e stated above, winds aloft is a much bigger consideration than any change in TAS.  

Edited by DanM20C
  • Like 1
Posted
I fly a stock 'C' and I try to load the plane to give me an aft CG.  90% of the time I cruise at 9,10, or 11K.  At 9K I usually see 141-142ktas.  At 11K I see 140ktas,  I have flown it at 15K twice and saw 135ktas and 137ktas.  So speed does drop off a little.  Like Ragsf15e stated above, winds aloft is a much bigger consideration that any change in TAS.  

I've been playing with aft CGs since the Summer. My plane is an honest 150 KTAS plane based on the 24 years of flying her. I have noticed at times I have squeezed a few more knots out but never really tried to figure out why. I started paying attention to the loading, including actually using my airport scale to check weights.

As Dan points out, aft CG does have an impact on airspeed. I am seeing as much as 4 knots increase with 80 or so pounds loaded in the baggage area.

Sent from my iPad using Tapatalk

  • Like 2
Posted
 

I am seeing as much as 4 knots increase with 80 or so pounds loaded in the baggage area.

I bet you're not having any trouble finding ballast amongst your harem!   :lol:

  • Like 1
Posted
 

I bet you're not having any trouble finding ballast amongst your harem!   :lol:

I white knuckle-resisted the urge to go there, only to have this happen...I have a feeling this thread is about to be unrecoverably stalled :blink:

  • Like 1
Posted
  I am seeing as much as 4 knots increase with 80 or so pounds loaded in the baggage area.

I bet you're not having any trouble finding ballast amongst your harem!   :lol:

The big challenge has always been to fit one of these:

66a1aa044ec3a8b1fe6f16985fdbf80d.jpg

Into something the size of this:

fdb164880e591cf8df912beef8401fdc.jpg

Sent from my iPad using Tapatalk

Posted
  I bet you're not having any trouble finding ballast amongst your harem!   :lol:

I white knuckle-resisted the urge to go there, only to have this happen...I have a feeling this thread is about to be unrecoverably stalled :blink:

Sorry Dev. You called it.

Sent from my iPad using Tapatalk

Posted

The modest speed gain from cramming that lady in the back will stall-spin ones libido into a smoking crater, if not the actual aircraft itself.  A cautionary tale for the speed-obsessed Mooney community. 

  • Like 1
Posted
 

As Dan points out, aft CG does have an impact on airspeed. I am seeing as much as 4 knots increase with 80 or so pounds loaded in the baggage area.

If you slide your seat all the way back you can usually grab 1-2 knots on that as well depending on where your CG loading is at.

 

 

  • Like 1
Posted
 

I did 650 nm and all of it between 12,500 and 16,500 in my C a couple of weeks ago.  I was getting between 150 and 155 knots TAS. But that's pretty much what I get all the time.

Could you please list all your speed mods, this seems significantly higher than any published data for stock "C's"

Posted
 

10500 full fuel 2 of us with about 75lbs baggage based on conditions (IAS OAT ALT) 147KTAS

My POH says at 10,000', standard day, standard plane, you have to run 2700 RPM (74.9% power) to get 142-146 kts.

What mods do you have?

Posted
 

My POH says at 10,000', standard day, standard plane, you have to run 2700 RPM (74.9% power) to get 142-146 kts.

What mods do you have?

cowl closure gap seals I think is all, oh yes! I forgot the big Kahuna I have the LASAR landing light cover

  • Like 1

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