Would like to know what owners see for indicated and true airspeeds and fuel flows at different altitudes and power settings. I normally flight plan mine between 16k and 17k at 185kts at a power setting of 29in manifold and 1800rpm. Fuel is about 37 gph.

It's been a while, but from memory I flew in the low 20s, 208tas, 45gph

I am usually a bit higher power setting up high.

31" and 1800-1750 RPM. About 21.7-22.5 gph per side. 75 ROP on the single factory EGT.

It varies with altitude. Down at 16,000 about 195-200 knots and about 210-215 at FL210 depending on load.

If ATC keeps me low 5000-7000ft I run a lower power setting maybe 27". not as concerned with mixture because I am typically getting vectored around but it would be about 18GPH a side.

https://web.archive.org/web/20120508044 ... 20Ops.html

Here is a the best rundown of 421 ops I have ever read.

The fuel burn numbers and range are a bit optimistic but the rest works out.

I used to use the lower RPM 1725 but reading TCM guidance 1800 is the least stress on the crankshaft. About 63% power setting I believe is best compromise between speed, fuel burn and time on airplane/engines.

Hal Stoen also had a good article on crashing his first 421 due to the old style boost pump switch setup and confusion over failing at high boost due to too rich and wrap around original fuel flow gauges.
https://web.archive.org/web/20120704032 ... 0Xray.html

I have about 1000 hours in a 1974 421B. Loved the plane and how quiet it was.

I mostly ran it LOP in the low flight levels, 19-22k feet. MP around 32-33, RPM 1800 and fuel flows at 17-18GPH a side. I would normally see around 200-205kts TAS at that settings. (Attached picture shows TAS in mph.)

Hilgard

There is a scary number of people flying tip tanked Twin Cessna's that do not understand the fuel system. I've seen multiple examples on social media sites from people flying them that have no clue if they have the couple Service Kit's installed, which make a big difference in how the pumps should be operated. Some of those people are self proclaimed experts that have flown the same airplane for years. There are scenarios where you can do thousands of dollars of damage to fuel pumps by not understanding what is happening. You can usually start the conversation by asking where is the aux inline fuel pump and when does it function on your airplane. That's when the deer in the headlights look starts...

Thank you for all the info. I feel like my aircraft is slower than others. Wondering if it’s antennas, control rigging, or something else. I have a recent paint job and keep it washed and waxed.

Could be an indication problem, ie. ASI is under reading due pitot or static issue.

Do you use the TAS/Wind calc page on the GNS or GTN ? Of course you need to be pretty sure of the prevalent wind predictions but if you systematically are seeing tailwinds then that would point to a indication problem.

[/quote]

There is a scary number of people flying tip tanked Twin Cessna's that do not understand the fuel system. I've seen multiple examples on social media sites from people flying them that have no clue if they have the couple Service Kit's installed, which make a big difference in how the pumps should be operated. Some of those people are self proclaimed experts that have flown the same airplane for years. There are scenarios where you can do thousands of dollars of damage to fuel pumps by not understanding what is happening. You can usually start the conversation by asking where is the aux inline fuel pump and when does it function on your airplane. That's when the deer in the headlights look starts...[/quote]

In the 1971 421B I was flying it had aux tank pumps that ran when the boost pump switches were in low. The problem was if you ran the aux tanks dry or very near dry the aux boost pumps would still run when you were on main tanks and boost pump switches in low. So if I ran the aux tanks down I would pull the aux tank boost pump breakers to prevent burning up the pumps the rest of the flight.

The 1974 I am flying now the aux tank boost pumps come on when aux tanks are selected regardless of the boost pump switch position and shut off when mains are selected. Even with boost pump switch on low. So no need to pull breakers anymore.

Little things that can make a big difference when jumping between similar airframes. But to find out sit in the hangar. Pull the landing light breakers to shut off the clicker pumps in the tips. Then select aux tanks and listen for the aux pumps to turn on.
Also pull the main pump breakers and then turn the boost pump switches to low and listen for aux pumps.

Nacelle tank pumps can be minutes different in speeds to empty the nacelle tanks and run dry also. Knowing the airplane helps.

I've never flown one with a nose tank. That would be a bit much I think.

Could be an indication problem, ie. ASI is under reading due pitot or static issue.

Do you use the TAS/Wind calc page on the GNS or GTN ? Of course you need to be pretty sure of the prevalent wind predictions but if you systematically are seeing headwinds then that would point to a indication problem.

There is a scary number of people flying tip tanked Twin Cessna's that do not understand the fuel system. I've seen multiple examples on social media sites from people flying them that have no clue if they have the couple Service Kit's installed, which make a big difference in how the pumps should be operated. Some of those people are self proclaimed experts that have flown the same airplane for years. There are scenarios where you can do thousands of dollars of damage to fuel pumps by not understanding what is happening. You can usually start the conversation by asking where is the aux inline fuel pump and when does it function on your airplane. That's when the deer in the headlights look starts...[/quote]

In the 1971 421B I was flying it had aux tank pumps that ran when the boost pump switches were in low. The problem was if you ran the aux tanks dry or very near dry the aux boost pumps would still run when you were on main tanks and boost pump switches in low. So if I ran the aux tanks down I would pull the aux tank boost pump breakers to prevent burning up the pumps the rest of the flight.

The 1974 I am flying now the aux tank boost pumps come on when aux tanks are selected regardless of the boost pump switch position and shut off when mains are selected. Even with boost pump switch on low. So no need to pull breakers anymore.

Little things that can make a big difference when jumping between similar airframes. But to find out sit in the hangar. Pull the landing light breakers to shut off the clicker pumps in the tips. Then select aux tanks and listen for the aux pumps to turn on.
Also pull the main pump breakers and then turn the boost pump switches to low and listen for aux pumps.

Nacelle tank pumps can be minutes different in speeds to empty the nacelle tanks and run dry also. Knowing the airplane helps.

I've never flown one with a nose tank. That would be a bit much I think.[/quote]

But you are smarter than the average bear! You know exactly what I was talking about. Then additional confusion comes with MEB88-3.

There are still airplanes in the wild without either of the mod's done. I just did them on my (previous) 414 about three years back.

Yes the 71 I was flying did not have MEB88-3 and it bit me one day. When I picked the airplane up in Oregon I noticed it had the old style boost pump switches. The seller and his son had owned the airplane for many years and I asked why they did not have it done. They said they weighed the risks and liked having the boost pumps able to auto switch to high if they had an engine driven fuel pump failure on takeoff. Ok fair enough. That is how it was originally designed. I knew the failure Hal Stoen had had and why also so I figured if I was aware it would be fine.

The airplane had the original mechanical fuel flow gauges removed back in the 70s and a Hoskins fuel flow meter installed. Similar function and transducers to a Shadin Digiflow but I actually liked the Hoskins better after using it a while.

Whoever installed the transducers routed them with a loop in the line so it would get vapor locked if you shut down after a flight and the engines were hot. Purging and starting hot was ok but there could still be air trapped that would not show up until you added power for a runup.

On this day I was at White Plains HPN and it was a hot day. I taxied to the north end and we were delayed a while after the runup. Suddenly the tower announced that we were cleared for a no delay takeoff and traffic on final. Ok sure so I went out and brought the throttles up for a rolling departure. Moving both switches up to "ON" position. Which was basically arming HI boost.
Into the takeoff roll and the trapped air hit the pressure switches, Both pumps locked to HI and both engines quit. I knew there was traffic behind and what had happened, controller was talking mile a min, so I pulled the throttles back, put both boost pump switches OFF then down to LOW and hit both starter buttons at once. Both engines caught and I worked the power back up to continue the takeoff. Pax never seemed to notice... I don't believe it would have happened except for the loops in the lines for the flow transducers.

So yes I would consider MEB88-3 mandatory . Later mechanical flow limiters should keep it from making pressure high enough the engines would quit if adjusted correctly.

I also rerouted the transducer lines to not have vertical loops but hose location and routing is a problem on these installations with aftermarket fuel flow meters.

The current 421 I am flying has the transducers mounted hard to the rear engine baffle bulkhead fittings. I'm not really crazy about the fittings they used and how they are mounted only on one end to the outlet fitting. But to mount transducers mid line and keep the lines away from hot parts is not really easy either. The transducers make a large non flexible area which causes other issues.
Anyone have example photos of their engine installations to show how the flow transducers were mounted and hoses routed?

This is the 421C that I used to manage. Right engine, propeller to the right.



The 414 I just sold was mounted very similar. I'll take a picture of the 421C that I'm buying when I see the cowl off in a few weeks.

Yes that is exactly what I am trying to fix. The B model is different at the back of the engine with no hydraulic drive and the hose and flow meter attached to one end of an unsupported stainless line made me concerned about the flare of the line breaking.

The hose routing on my setup would require a very short hose on the forward side of the transducer where the hose ends would be almost touching with very little flex hose exposed in between.

All depending on the strength of the pipe thread fitting threads on the flow meter. I guess it works but I'd rather the flow meter be in between two flex hoses or the hoses clamped somehow to take the stress off the flow meter fittings.

Charlie, take a look at the Insight G4 Twin installation manual. It shows the transducer mounted on the backbone of the engine. I don't know if that would work in the 421 with the overhead intake or now. I believe Guy was manufacturing a mount for normal IO/TSIO engines. Page 43 and a few after that give some good ideas..

https://www.insightavionics.com/pdf%20f ... 20v1.6.pdf