Mooney M-18 Performance

[Kevin Harberg]

Hello everyone,

Just wondering if  the gap seals (ailerons, flaps, horizontal stab, vertical stab) as well as other modifications that Denver Jacobson did on the build of C-GXTR (M-18X) was worth the effort. It appears to me that this Continental A-65 powered Mite is at least as quick as book (and climbs like crazy), even with the 1025lb gross weight licensed by Transport Canada in the homebuilt/experimental category. The attached photo shows 116-117mph IAS @2150RPM cruise at 3650'ASL (5-10MPH tailwind component as displayed on GPS). On occasion with short bursts of full power (15 seconds max), I get an IAS of 135mph and once had seen VNE in level flight. I have also attached a photo of GPS max ground speed in level flight (with a real strong tailwind, full rich, full throttle short duration). The reason for the post is to determine average cruise numbers of the light weight Lycoming powered M-18's compared to the heavier stock Continental powered M-18's (and to the highly modified M-18X, C-GXTR).

Blue Skys!

 

Kevin Harberg

 

[carusoam]

Gap seals became a standard in production over the years...

Expect that they can work...

The faster the plane, the more value they have...

Great to see a Mite post!

Best regards,

-a-

[Mooneymite]

Kevin, I'm not familiar with that experimental version of the Mite, but I am curious that it seems to have neither the wig-wag gear indicator, nor gear lights.  What am I missing?

[Kevin Harberg]

On 3/20/2020 at 6:56 PM, Mooneymite said:

Kevin, I'm not familiar with that experimental version of the Mite, but I am curious that it seems to have neither the wig-wag gear indicator, nor gear lights.  What am I missing?

If you zoom in, you will see the big red light is labelled on its left as landing gear. The large size was chosen so as to be to be visible during the high ambient daylight conditions observed at noon through the canopy (greenhouse effect washes out smaller indicator lights placed higher up on the panel). The indicator light is actuated via "gear down" detent mounted micro switch interlocked (in series) with the throttle idle micro switch. The size reminds me of a stall warning light I have seen in other aircraft.

[Mooneymite]

Ahhhhhh.  Thank you.

I always thought the vacuum wig-wag was a clever idea, though it was apparently no more successful than other gear warning systems.  Lots of Mites landed gear up.

My Mite had the lights, but they were abysmally dim.  If I remembered to check the lights, it was because I had already remembered to lower the gear.  

[Sblack]

What made this m18x come out at 1025 lbs? I thought the empty weights were more like 850 lbs. 

[Kevin Harberg]

On 8/27/2020 at 11:55 AM, Sblack said:

What made this m18x come out at 1025 lbs? I thought the empty weights were more like 850 lbs. 

This M18X uses the metal fuselage design of the M18X Mooney Mite plans with an additional bulkhead installed by the fuel tanks. The stringers are heavier than specified and tie into the rearmost bulkhead from a Mooney M20A (the bulkhead that the entire tail section pivots on to adjust nose up/nose down trim). The vertical stabilizer spar is reinforced with a doubler on the lower section. The vertical stabilizer trailing edge is double the stock thickness. The horizontal stabilizer spar is reinforced with a doubler in the centre section. The horizontal stabilizer trailing edge is double the stock thickness. The one piece wing is fully covered top and bottom in Finland Birch aircraft grade plywood similar to the Mooney M20A. Gear modifications for increased gross weight include build up of the upper nose gear support truss and installation of Cessna 150 axles with larger 5:00 X 5 wheels. Many other upgrades, some for strength and some for speed.

Canadian Department of Transport at the time of certification utilized a formula with wing area and Time To Climb Tests to determine gross weight.

Regards,

 

Kevin H.

[carusoam]

Great details, Kevin!

Thanks for sharing them...

Best regards,

-a-

[Kevin Harberg]

Still not fast enough? With Mooney's clean lines, all that's required to boost cruise numbers appears to be horsepower. Consider the Mooney Mite's performance with 85-90Hp. 85Hp M-18's are reported to have economy cruise speeds of 145mph while the 90Hp M-19 was reported to cruise at 150mph. Not bad for a 1946 design! Not the 2mph per horsepower (@75% and optimum altitude) of the 65Hp models but quite impressive just the same.

[Kevin Harberg]

Here's Mooney's advertised specifications for the M-18LA and M-18C

[Walt]

Kevin,

I enjoy your Mite posts. I am rebuilding #231 and have a 90hp RR engine for it and want to increase the Gross Weight (for reasons best left at the dinner table).  I have a copy of Al Mooney's original design specs for the M19 and it clearly specifies a fully wood covered wing and higher GW increase than C-GXTR has.  I do not want to   put 231 in the experimental class (I have a copy of a 337 for the engine from the FAA).  Most of the other changes you described in your Sept 25, 2020, post have already been made in accordance with Mooney Service Bulletins and FAA AD's.

What I would like to know is do you have copies of the original specs authorized by Canadian DOT and the authorization for the full wood covered wing.  It may help with the FAA based on reciprocity.  I have also consulted with a DER who is favorable to the change.  However, the A&P feels that the FAA will want more.

Thank you

Walt Ayers

[carusoam]

Hey Walt!

Let’s invite @Kevin Harberg to stop by…

Best regards,

-a-

[Kevin Harberg]

11 hours ago, Walt said:

Kevin,

I enjoy your Mite posts. I am rebuilding #231 and have a 90hp RR engine for it and want to increase the Gross Weight (for reasons best left at the dinner table).  I have a copy of Al Mooney's original design specs for the M19 and it clearly specifies a fully wood covered wing and higher GW increase than C-GXTR has.  I do not want to   put 231 in the experimental class (I have a copy of a 337 for the engine from the FAA).  Most of the other changes you described in your Sept 25, 2020, post have already been made in accordance with Mooney Service Bulletins and FAA AD's.

What I would like to know is do you have copies of the original specs authorized by Canadian DOT and the authorization for the full wood covered wing.  It may help with the FAA based on reciprocity.  I have also consulted with a DER who is favorable to the change.  However, the A&P feels that the FAA will want more.

Thank you

Walt Ayers

Hello Walt,

I have found C-GXTR's Transport Canada Application To Construct Amateur-Built Aircraft. It shows the Allowable Gross Weight per E & I Manual to be 1431lbs and a Max Requested weight of 1025lbs (which was granted after I completed the Climb Test Report). The 1025lb requested weight permited the finished empty weight of 683lbs plus a 165lb pilot plus 29.5 gallons of fuel. The wing construction information indicates "Birch plywood similar to S.T.C. SA2-1053 (Mooney M-18 N-383A) by Frank Poplawski, Route 3, Ennis Texas". I could email you copies of Transport Canada allowable gross weight calculations and accompanying Climb Test Report for your perusal if you wish to message me (via Mooney Space Messages).

Have a good one!

Kevin Harberg

 

[Walt]

Kevin,

In one of your messages you mentioned, " The wing construction information indicates "Birch plywood similar to S.T.C. SA2-1053 (Mooney M-18 N-383A) by Frank Poplawski, Route 3, Ennis Texas". " Is it possible to trouble you a copy of this as well?  I am looking for a copy of this statement and where it is located for the chain to be able to show it is the same as in the E&I.  The FAA can be sticklers on this type of thing. The actual STC I am trying to get from the FAA.

I got all eleven of E&I. Thanks Again,

Walt

 

 

 

[Kevin Harberg]

On 1/19/2023 at 12:57 PM, Walt said:

Kevin,

In one of your messages you mentioned, " The wing construction information indicates "Birch plywood similar to S.T.C. SA2-1053 (Mooney M-18 N-383A) by Frank Poplawski, Route 3, Ennis Texas". " Is it possible to trouble you a copy of this as well?  I am looking for a copy of this statement and where it is located for the chain to be able to show it is the same as in the E&I.  The FAA can be sticklers on this type of thing. The actual STC I am trying to get from the FAA.

I got all eleven of E&I. Thanks Again,

Walt

 

 

 

Hello @Walt

I will send what I have via your e-mail (as you sent me via Mooney Space Messages) 

Regards, 

 

Kevin Harberg

[Mcstealth]

On 1/19/2023 at 1:57 PM, Walt said:

Kevin,

In one of your messages you mentioned, " The wing construction information indicates "Birch plywood similar to S.T.C. SA2-1053 (Mooney M-18 N-383A) by Frank Poplawski, Route 3, Ennis Texas". " Is it possible to trouble you a copy of this as well?  I am looking for a copy of this statement and where it is located for the chain to be able to show it is the same as in the E&I.  The FAA can be sticklers on this type of thing. The actual STC I am trying to get from the FAA.

I got all eleven of E&I. Thanks Again,

Walt

 

 

 

Good luck. Hope it works out.