98 Allegro vs 1980 M20J

[Tx_Aggie]

Also on the topic, I’ve read a few threads on the not so well designed ram air function in the J, from the factory. While reading up on the performance of the Ovation in several mid1990’s aopa/aviation consumer articles one author noted the improved performance due to tuned induction on ram air by 1-1.5”… I know there’s no “ram air” lever on the ovation but it caused me to think about how to either improve the ram air on my J - I know most people seal it up nowadays or if it’s worth testing out some of the newer air filter designs. There are some recent threads on that also (Donaldson, champion and bracket - which is installed on mine.)

anyone with the “newer” Lopresti SCRAM cowling care to chime in on Ram air tubing design?

 

Mooneys Dunbar said that much effort went into the induction system to achieve even fuel distribution with ram air recovery totaling 1 to 1.5 inches.

https://www.aviationconsumer.com/used-aircraft-guide/mooney-m20r-ovation-mods/

[Fly Boomer]

7 hours ago, Mooney in Oz said:

Beware of marketing speed claims.

The technical term is IAS (Internet Airspeed).

[Pinecone]

9 hours ago, 1980Mooney said:

Actually tubby.  The 252 empty weight was 1,800 lbs.  The Encore empty weight was 2,000 lbs. - 11% heavier than a 252.    Only because Mooney increased the GW on the Encore to 3,130 lbs was the Encore able to carry more than 2 pax.  

Which is why a 252 converted to Encore is so nice.

 

[KSMooniac]

4 hours ago, Tx_Aggie said:

Also on the topic, I’ve read a few threads on the not so well designed ram air function in the J, from the factory. While reading up on the performance of the Ovation in several mid1990’s aopa/aviation consumer articles one author noted the improved performance due to tuned induction on ram air by 1-1.5”… I know there’s no “ram air” lever on the ovation but it caused me to think about how to either improve the ram air on my J - I know most people seal it up nowadays or if it’s worth testing out some of the newer air filter designs. There are some recent threads on that also (Donaldson, champion and bracket - which is installed on mine.)

anyone with the “newer” Lopresti SCRAM cowling care to chime in on Ram air tubing design?

 

Mooneys Dunbar said that much effort went into the induction system to achieve even fuel distribution with ram air recovery totaling 1 to 1.5 inches.

https://www.aviationconsumer.com/used-aircraft-guide/mooney-m20r-ovation-mods/

@testwest did extensive drag-reduction on his former '77 J and I would bet that it is the most aerodynamically refined J in the fleet.  You can search up his posts over the years for more detail, but he maxed-out hiding antennas under fiberglass, LoPresti Cowl, Hartzell Top Prop, Powerflow exhaust, 1-pc belly, wingtips, rigging, etc. and the resulting optimized cruise was 165 KTAS at 11k at 10 GPH with the LoPresti ram air open.  The J Powerflow is optimized for high cruise, ~11-12k, for some reason, instead of the traditional J optimal altitudes of 7-9k IMO, and if I were king I would have tuned it for that alitude range and perhaps eeked out a few more knots.  (Their C/D/G system seem better across all altitudes, though, according to anecdotal reports.)

For more ideas, search up the CAFE Foundation super-modified E model and look at what they accomplished!  Unfortunately those mods were R&D/Experimental and not available as an STC.  Someone adventurous could perhaps pursue a similar course as an STC project, though.

[1980Mooney]

This was just discussed last month. WAT (Whelen) which bought LoPresti 4 years ago. They no longer show the Mooney cowl for sale (they still sell Piper cowls). When it was for sale it was $16k plus $5k install and it needs paint. I bet if they were to fan one today it would be way more (like every thing in aviation).  If you are actually considering paying $25k+ for a cowl you might be better just buying a better plane….or an overhaul….or an IO-390….

 

[PT20J]

4 hours ago, Tx_Aggie said:

Also on the topic, I’ve read a few threads on the not so well designed ram air function in the J, from the factory.

I think that's backwards. The reason the ram air is not as effective on the early M20Js compared to earlier models is that the induction system is much more efficient on the J and so there is less to improve. The ram air is directed at the air intake of the servo and it would be difficult to think of a better design without eliminating the air filter plenum completely. On my 1978 J, the ram air was good for about half an inch of MAP, maybe a little less.

[Tx_Aggie]

24 minutes ago, 1980Mooney said:

This was just discussed last month. WAT (Whelen) which bought LoPresti 4 years ago. They no longer show the Mooney cowl for sale (they still sell Piper cowls). When it was for sale it was $16k plus $5k install and it needs paint. I bet if they were to fan one today it would be way more (like every thing in aviation).  If you are actually considering paying $25k+ for a cowl you might be better just buying a better plane….or an overhaul….or an IO-390….

 

I like the io-390 idea but what does an overhaul cost these days, $35-40k? I don’t know. 

[ArtVandelay]

On my 1978 J, the ram air was good for about half an inch of MAP, maybe a little less.

On my 78 I think it was less, the analog gauge moved but not much. Don’t forget once you remove it you won’t have the unsightly hole creating drag. I believe the reduction of drag will compensate for the ram air.

[Mooney in Oz]

4 hours ago, ArtVandelay said:

Don’t forget once you remove it you won’t have the unsightly hole creating drag.

You also won’t have to worry about the engine stopping if you forget to close the ram air when inadvertently entering icing conditions.

Ask me how I discovered this .

Ram air removed thereafter.

 

 

[A64Pilot]

There is a diminishing point of return for anything, the J as it comes from the factory is at or beyond that point, in my opinion, there just isn’t any easy speed left.

Can you get more speed? Sure a little, but at an ever increasing price point, is 1 kt worth $1,000? How about $10,000? To some it is.

In all honesty the way to go faster is to significantly reduce airframe drag, the most tried and true way to do that is by reducing air density with altitude, then add back the HP the engine lost by increasing air density for it.

My J can on any given day squeak out 168 kts true, at 1,000 MSL and burning 17 GPH, but I’d never cruise it that way myself

[A64Pilot]

I don’t know why winglets came up but they only work at high angles of attack, believe it or not but the average airliner flies at altitude a lot closer to stall than we may think, so at a high, near critical angle of attack, where wing tip vortices are large, so they in fact do decrease drag.

But on GA aircraft that don’t cruise anywhere near critical angle of attack they at best only look cool, because they do increase drag. In truth on average GA aircraft simply ending the wing as on older Mooney’s is about as good as anything else drag / speed wise, you can prove elliptical wing tips and Hoerner wing tips on paper, but I don’t think they amount to much on the airplane.

I don’t know how winglets could increase gross weight, can someone enlighten me on that?

 

[KSMooniac]

If the effective span extension of a winglet could provide enough extra lift to reduce stall speed on a plane that is limited by stall speed, then I could envision a GWI just due to winglets.  I can't imagine it would be substantial, though, because it would also increase the maximum bending moment on the wing, and that might require a corresponding increase in structural weight as well.  I believe current Mooneys are GW-limited due to the landing gear and drop test performance, and not quite bumping up against the 61 knot stall speed limit.  Say they eventually get the new gear out and go to 3600 lb max gross... if the stall speed goes to 62 knots perhaps a new wingtip might be able to bring it down to 61 knots or lower.  We all know the Mooney wing has excess structural capacity, so it could probably be done without any mods inboard to the wing tip attachment.  Just my hunch as a structural analyst in the industry...

[PT20J]

No idea why we are discussing winglets here either  -- the Mooney sculpted tips are NOT winglets. As noted above, the idea was primarily to get the tip vortex outboard of the aileron to reduce control forces. The shape is most likely for aesthetics rather than aerodynamics. 

Winglets were invented by Richard Whitcomb and found their place in high sub-sonic jets, often to reduce cruising induced drag of older designs. BTW, while wingtip treatments can reduce induced drag by altering the vortices, elimination of the vortices is impossible for a finite length wing as described by Doug McLean in Understanding Aerodynamics. Modern clean sheet designs seem to favor other more aesthetic solutions such as the Boeing 787's raked wingtips.

Here is Whitcomb's 1976 paper describing winglets in detail...

Skip

19760019075.pdf

[A64Pilot]

Actually wing tip vortices can be nearly completely eliminated, but the device tested that did so on Agricultural aircraft in the NASA wind tunnel years ago actually increased drag.

The swath width of the spray in an Ag plane is limited because make the spray booms wider and the spray gets caught up in the vortices and results in “off target application” or drift so elimination of the wingtip vortices even if drag is increased could greatly increase its productivity.

These unfortunately don’t really do anything, but can significantly reduce wing spar life, by how much hasn’t been determined

https://www.johnstonaircraft.com/Ag Tip Winglets.htm

[aviatoreb]

Clip the wings - shorter wings less drag. Just don't tell anyone...

Edited January 14, 2023 by aviatoreb

[PT20J]

 

9 hours ago, aviatoreb said:

Clip the wings - shorter wings less drag. Just don't tell anyone...

Shorter span increases induced drag but reduces parasite drag to the extent that the wing area is decreased.

[PT20J]

Trying to reduce induced drag by messing with the wingtip vortices alone is doomed to failure because the vortices are not the cause of the drag but rather an effect of the airflow around the wing. Finite length wings shed a vortex sheet that creates a downwash and this is the source of the drag. (The downwash has the effect of tilting the lift vector aft. This vector can be decomposed into a vertical component that offsets the aircraft weight keeping the aircraft aloft, and a horizontal component which is the induced drag). The longer the wing, the less the downwash and the weaker the vortex. An infinite length wing has no downwash, vortices or induced drag. The shorter the wingspan, the greater the downwash, vortices and induced drag. 

The reason the Reno racers clip the wings is that at high speed they don't need as much wing area for lift (recall that lift is proportional to both the wing area and the square of true airspeed) which causes parasitic drag. The simplest way to decrease the wing area is to shorten the wing. At race speeds, the tradeoff in increased induced drag caused by the shorter span and decreased drag due to the reduced area is beneficial. They pay for this in higher landing speeds, however, which is why it doesn't work for a Mooney.

Skip

[carusoam]

On 1/9/2023 at 5:07 PM, Mooney in Oz said:

You also won’t have to worry about the engine stopping if you forget to close the ram air when inadvertently entering icing conditions.

Ask me how I discovered this .

Ram air removed thereafter.

 

 

You are not the only one to report this issue…

An MSer from the UK learned about ram air and icing over the North Atlantic…

 

The only reason why I am familiar with the issue….  Newer Mooney intake systems have been modified to keep intake clogs from stopping the engine…

I think they call it an ice door…

You get to read about all the things it solves… but, at the same time… it is really hard for owners of the older machines to be aware of the pitfalls…

 

Go MS!

Best regards,

-a-

[PT20J]

I believe that the icing risk with ram air is due to the fact that ice laden ram air can plug the impact tubes in the inlet of an RSA fuel injector servo. 

[Pinecone]

10 hours ago, PT20J said:

The reason the Reno racers clip the wings is that at high speed they don't need as much wing area for lift (recall that lift is proportional to both the wing area and the square of true airspeed) which causes parasitic drag. The simplest way to decrease the wing area is to shorten the wing. At race speeds, the tradeoff in increased induced drag caused by the shorter span and decreased drag due to the reduced area is beneficial. They pay for this in higher landing speeds, however, which is why it doesn't work for a Mooney.

Skip

Formula 1 air racers did that, until Nemesis came out and showed that a longer wing was actually faster around the course due to turn performance.

[aviatoreb]

11 hours ago, PT20J said:

 

Shorter span increases induced drag but reduces parasite drag to the extent that the wing area is decreased.

I agree completely.  I know it would ruin the wonderful flying characteristics and surely be impossible within a certified scenario, not least of which significantly increased stall speed, but it surely would result in a faster airplane.  I was just pointing out something for curiosity sake.

[0TreeLemur]

On 1/12/2023 at 1:19 AM, PT20J said:

No idea why we are discussing winglets here either  -- the Mooney sculpted tips are NOT winglets. As noted above, the idea was primarily to get the tip vortex outboard of the aileron to reduce control forces.

 

After 5 years of flying a C and now flying a J, I can attest that getting the tip vortex off the aileron makes the J feel much more nimble in roll compared to the C.

[PT20J]

6 minutes ago, 0TreeLemur said:

After 5 years of flying a C and now flying a J, I can attest that getting the tip vortex off the aileron makes the J feel much more nimble in roll compared to the C.

I owned a 1978 J (squared off wingtips) 30 years ago and now own a 1994 J (sculpted wingtips). It's been too long for me to compare aileron forces, but I did notice something else:. In the older airplane, both ailerons tended to float up a slight bit during cruise, and I don't notice this with the later model.

[PT20J]

3 minutes ago, bluehighwayflyer said:

I believe that is just a function of wear in the helm bearings.  I didn’t notice a difference in aileron forces between my C and my previous ‘78 J.  They both are very heavy in roll to my liking.  Maybe the wingtips and aileron gap seals on the later models help.  

Possibly. The 1978 was only 7 years old when I bought it and had about 1000 hours total time. The 1994 was 24 years old with about 1200 hours total time when I purchased it. Neither seemed to have much lost motion in the controls, though, but I don't have the two airframes together to compare.

All the Mooneys are heavy in roll because the ailerons are wide in chord and short in span to get the required area while giving more wingspan to the flaps. The greater chord increases the hinge moment. Also, the control wheel has less mechanical advantage than most other airplanes.

When comparing the older models it is also important to note whether the ailerons have beveled trailing edges. I believe the bevel (a standard method to reduce control force) was added when the PC system came out to make it easier for the servo to manipulate the ailerons.

Skip

[DCarlton]

4 minutes ago, PT20J said:

Possibly. The 1978 was only 7 years old when I bought it and had about 1000 hours total time. The 1994 was 24 years old with about 1200 hours total time when I purchased it. Neither seemed to have much lost motion in the controls, though, but I don't have the two airframes together to compare.

All the Mooneys are heavy in roll because the ailerons are wide in chord and short in span to get the required area while giving more wingspan to the flaps. The greater chord increases the hinge moment. Also, the control wheel has less mechanical advantage than most other airplanes.

When comparing the older models it is also important to note whether the ailerons have beveled trailing edges. I believe the bevel (a standard method to reduce control force) was added when the PC system came out to make it easier for the servo to manipulate the ailerons.

Skip

Beveled trailing edges?