PT20J

It is important to understand that the GFC 500 architecture is different from other autopilots. Most autopilots have a computer that gets inputs from the the attitude gyro and the directional gyro or HSI and compute solutions to drive the servos. The GFC 500 is different. Most of the software is actually in the G3X or G5 or GI275 and some of it is in the "smart" servos. There is no separate computer. That's why the GFC 500 will not work with an Aspen.

The iPad gets it's data from the GTX 345.

I have a mini mounted on the yoke. I don't usually bother with it for local VFR flights -- everything I need is on the G3X and GTN. When flying VFR, I keep the GTN on the traffic display and when flying IFR I keep it on the Flight Plan page. I use the iPad with ForeFlight for longer flights and for IFR flights. 1. I can do the flight planning on it, file the flight plan with it and upload the flight plan to the panel via Bluetooth. 2. It provides a larger display for the approach plates than the G3X split screen. 3. I find it easier to maneuver around ForeFlight to check on weather and also do what if planning. 4. I like the weather overlays on the ForeFlight map and especially the ability to increase the transparency so that the radar doesn't obliterate the other map features. 5. It provides instant redundancy should the G3X fail. I tried using the iPad on my lap, but I have a tendency to rest my hands there and I was always touching the screen and causing the display to change to something other than how I left it.

For your second question, it will be dictated by what the STCs for the Aspen and G5 allow. I don’t know if Aspen will allow a G5 to replace any backup instruments. The G5 STC only allows it to replace an AI, HSI or turn coord. And you’re going to have to ditch the Aspen if you install a GFC 500 because the autopilot needs a Garmin display to drive it and that display must be primary.

Deakin’s take on climb speeds. https://www.advancedpilot.com/articles.php?action=article&articleid=1842 Airspeed and altitude are both forms of energy — airspeed being kinetic and altitude being potential — and are thus interchangeable (neglecting losses due to drag). But, conversion requires acceleration which has a time element. If you are close to the ground and descending, you don’t have a lot of time.

Vx should increase with altitude and Vy should decrease with altitude and they converge to the same speed at the absolute altitude. The chart shows Vy decreasing with altitude but doesn’t show Vx increasing. Looks like Mooney just picked one number and stuck with it.

200. Thrust required = drag, so lower drag will also reduce Vx. 94 mph seems way too high for Vx. Especially when Hank’s C is 80.

According to my 1994 M20J POH, clean, power off, gross weight, level flight stall speed is 62 KIAS and Vx at sea level is 66 KIAS. Best angle of climb is the speed where there is the maximum difference between thrust available and thrust required. The bigger the engine, the lower Vx. The F-15 supposedly has a thrust/weight ratio of 1.17:1, so it's Vx is zero.

The exhaust cavities are supposed two be sealed to the firewall, so you should reapply sealant when you reinstall them. My airplane doesn't have any parts requiring service in there. I loosen enough screws to insert a borescope in the area from the aft end to look around and check for any issues with the boost pump or brake master cylinders.

I find it easiest to remove the rod ends from the gear doors and then remove all the inboard screws and slip the doors off. Then you can just remove the rest of the screws attaching the exhaust cavities and take them off without anything in the way.

It looks pretty noisy even when it’s working. I’d first check all the connections carefully. O

That surprises me, also. Best glide occurs at the max L/D speed. In fact, the glide ratio is simply the ratio of lift to drag. Since lift = weight, it's also the minimum total drag speed. Total drag is comprised of induced drag (which decreases with airspeed) and parasitic drag (which increases with airspeed.) The minimum total drag occurs when each drag component is contributing half of the total. Since stopping the prop reduces parasitic drag, it should cause the minimum drag to shift to a higher airspeed, but the chart shows lower.

It took a lot of sleuthing and phone calls to Mooney to figure it out. The installations can be confusing because the installer has to read the installation manuals for each piece of equipment in the right order as some equipment installations require changes to wiring or configurations of other equipment.

I’ve heard lots of discussion about which is the lowest drag: windmilling vs stopped prop. According to this graph from Aerodynamics for Naval Aviators, it depends on blade angle. This agrees with data from an old NACA report I looked up once. What is apparent (and easily verifiable if you try it) is that pulling the prop control all the way back greatly improves glide. In my J, the rpm is in the yellow arc at best glide with the engine at idle and the prop set for 2500 rpm. The vibration reminds me to pull the prop control back.

In a G3X installation, all the audio is routed through the G3X GDU and the G3X installation manual calls for only the G3X to be connected to the audio panel. If the GTN is also connected, you will likely get an echo when engaging Smart Glide (that’s how I found out that both of mine were connected.

Sorry, but your installer doesn’t seem to know what he’s doing. The alerts should have been configured during installation. Assuming everything is wired correctly, enter configuration mode, go to the sound configuration page and set up the alerts.

Yes, the lift force can be derived as either a change in momentum or a change in pressure because the two are two sides of the same coin.

That's because that is a Mooney part number. If you want to order it from Mooney, call a MSC for price and delivery. But, McFarlane will almost certainly be cheaper.

That's a cool simulation. I did not see where it showed that there is a net downward momentum. I believe that Doug McLean addressed that fallacy at the end of his lecture and in more detail in his book. Both McLean's analysis and Lissaman's paper show that there is an updraft before the airfoil and a corresponding downdraft behind the airfoil and each accounts for 1/2 of the lift force. It occurs to me that there can be confusion with the term downdraft. There is downdraft behind even an infinitely long wing just as there will be an updraft ahead of the wing. But that's not the downdraft that people generally refer to when invoking Newton's third law to explain lift. The "Newton explanation" downdraft is the one that is not balanced by the updraft ahead of the wing and it is the source of induced drag, not lift. It is caused by a vortex sheet shed by a finite span wing. Details can be found in any aerodynamics textbook where induced drag is introduced.

Aircraft Spruce buys them from McFarlane. So does Mooney. I doubt anyone keeps them in stock but if McFarlane lists the part number then they should have a drawing for it and can make one without you having to send your old one to them.

It's going to be a Mooney part number and if you buy it from Mooney it's going to be expensive if they even have it. I would contact McFarlane and see if they have one. Worst case, you would send them your old one and they would make a new one to match it.

The important requirement for lift is that the average pressure above the wing be lower than the average pressure below the wing. This does not necessarily mean that the pressure below the wing is higher than the static air pressure.

This actually makes a great point. Camber is not necessary to generate lift. A flat plate will generate lift. The purpose of airfoil shapes is to generate lift efficiently which means minimizing the drag created by the wing. Drag takes on two forms: Parasite drag from skin friction which is reduced by minimizing the wing area thus necessitating so-called high lift devices on the leading and trailing edges in order to get lift at lower speeds for takeoff and landing; and, induced drag which is caused by the production of lift and can be reduced by careful airfoil design.

I am certainly not trying to argue with anyone and none of the ideas I have presented are my own. In fact, I presented two videos, one by a retired senior Boeing engineer and one by a professor of aeronautics, that essentially say the same thing albeit with much more detail and rigor. Here is a paper (for those who might be interested) written by a (now sadly deceased) well know aeronautical engineer. My only purpose in presenting this was to try to point out that a lot of what is presented in instructional materials for pilots is just plain wrong and it's not really that hard to understand what is really happening, at least at a very basic level. But I do understand the law of primacy and what we first learn sticks with us. But, for those with an interest, I think it is a fascinating subject to explore. So many things I thought I knew in my early flying career have been proven to be wrong and one reason I find aviation continually interesting is that there is always more to learn. The Facts of Lift - Lissaman.pdf

Maybe not zero, but not much more at cruise. From the attached curves I got long ago from Mooney, the Mooney wing zero lift angle of attack is -1 deg. So, because of the camber, it generates lift at zero. But, we can easily calculate it: L = 1/2 p V2 CL S Solving for CL and converting to convenient units at sea level on a standard day, CL = 295 W/V2S where, W = weight in lb., V = KTAS, S = wing area in ft2. For a M20J, S = 174.8 ft2. For our example, lets use 2500 lb weight at 150 KIAS: So, CL = 295*2500/150^2*174.8 = 0.1875 According to the attached curve, that corresponds to a angle of attack of about +1 deg. M20K Aerodynamic Coef - Flaps 0.pdf