Announcement

**kestrel** · 11-29-2022, 08:25 PM

Originally posted by Battson View Post

For the benefit of new builders reading this thread, I want to reiterate that there have been several near misses and at least one fatality in Bearhawk aircraft due to apparent mismanagement of the fuel system and / or not flying in balance, apparently causing a tank to unport, per this safety message from Bob (original thread post)

...and people also die from running out all their fuel before they realize that there is a problem. I'm not making this up. I'm also not asking you to change your methods. ...but your posts keep stating that everyone not doing it your way is wrong and stupid.

**Battson** · 11-29-2022, 09:00 PM

Originally posted by kestrel View Post

...and people also die from running out all their fuel before they realize that there is a problem. I'm not making this up. I'm also not asking you to change your methods. ...but your posts keep stating that everyone not doing it your way is wrong and stupid.

Let's have a conversation about risk levels, rather than getting emotive about it.

I have been quite clear that I support your right to do whatever you choose and make whatever risk / benefit tradeoffs you prefer. I would like to hear the counterview.

I want clarity, to avoid misinformed decisions. This has happened already, with the safety of real people jeopardized and actual engine stoppages which could have been avoided were clear information available. I am not saying this is anyone's fault, but it is an undeniable result of the lack of clear information.

**jaredyates** · 11-29-2022, 09:03 PM

Is this the Bearhawk version of the primer discussion among Vans builders? It is at least more consequential and worthy of discussion than whether or not to prime. But I don't see a clear path to consensus.

**kestrel** · 11-29-2022, 10:33 PM

Originally posted by Battson

I don't think we need consensus, and it would be a mistake to force it.

Originally posted by jaredyates

I don't think there is a single easy answer of one fuel management strategy that will apply to all Bearhawks

Originally posted by Battson

There will be many different system designs, each with it's own risks and advantages. I think the problem is, we are mixing them all into one discussion, and only those who are deeply studying the area understand what's going on. Clearly some people have a detailed understanding, which is great. However some will not grasp all the important points and we are seeing many people (outside the forum) struggle to make sense of it all.

I entirely agree with all three of these statements.

The problem I'm having is that more than one of your posts state that any conclusion other than yours is wrong.

I have complete confidence that my fuel system will deliver fuel and my engine will produce power if any of the 4 ports of which ever main tanks are selected as fuel at it. I've tested it. Others have done the same and with the same results. This is even true for Ed Meyers' EFII/System32 Patrol that pumps a lot more fuel through the lines. There may be fuel systems that won't do it. I'd suggest people test their systems to know, and consider redesigning them if they don't perform. If redesign isn't done, then plan and fly accordingly. For certified airplanes, this has been done for you.

I have much less confidence that we know what happened to the Bearhawks that have failed to restart when fuel was believed to have made available to the system. I've never seen detailed information about their fuel systems. I don't know what the pilot didn't know they didn't know. If they had been monitoring their fuel, we wouldn't need to wonder. If they had tested their systems more thoroughly, they might have found a problem sooner. There may have been something about their fuel systems that caused the failure to restart. Though variation in circumstances needs to be considered, I don't believe in random behavior of systems.

I don't know how many may have had issues that were made worse by running on both until there was, unexpectedly, no more fuel that would get to the engine. Regardless, the number of Bearhawks isn't that large and the number of relevant incidences is very small. The statistics aren't there to state that one type of failure is clearly the bigger problem.

I also don't believe that using "both" is a substitute for monitoring fuel levels (fuel totalizers aren't relevant here). I am absolutely certain that you are proficient and conscientious enough that you monitor yours. But several of your posts sound a lot like "both" is a magic fix and that no one ever crashed because they failed to notice that they had a problem until they had no fuel left that would flow to the engine.

The other variation on "none left", is "none left that will feed". People have also run on both until the fuel in the tank that would flow was run out. Either a plugged fuel pick-up or a plugged tank vent left them with only one tank flowing. Some early RV's could end up with fuel pick-ups that rotated in the tank and no longer reached the bottom.

A Lancair 4P crashed and killed the ferry pilot because the tanks weren't internally vented properly and air couldn't escape the top of the tank. The tanks never took the amount of fuel they were supposed to and no one ever tested it.

Since I am certain that you monitor your fuel levels, I have no doubt that you would notice if only one of your tanks was delivering fuel. There are numerous ways to figure it out.

I conclude from all of this that either strategy can work well if you have tested and are paying attention to the systems. If you have not tested or are not paying attention, either strategy can get you into trouble. The fuel selection strategy is essentially a red herring.

**Bissetg** · 11-29-2022, 11:00 PM

Hmmm …. There’s a lot going on here. I’m not very bright so forgive me if I’ve missed something.

my view is that the matters being discussed can be broken into separate elements.

1 Fuel system design and fitness for purpose (read is there a need to alter or modify?)
2 Management of the fuel system
3 Operation of the aircraft affecting the fuel system

But also important is Battsons previous post;

“I want to reiterate that there have been several near misses and at least one fatality in Bearhawk aircraft due to apparent mismanagement of the fuel system and / or not flying in balance, apparently causing a tank to unport, per this safety message from Bob (original thread post).“

This is exactly why we need a good reporting and recording and reference system in order that we can share the learnings from these events.

To address the fuel system elements as I see them.

1 The fuel system is absolutely fit for purpose in normal operating conditions. Nev has done extensive testing and me to a lesser degree to provide a sound understanding of what the Unporting risk poses to an injected engine. The B model Bearhawk with the factory supplied tanks has a very low amount of unusable fuel, less than 1 litre per side when I tested mine. The risk is not in Unporting one tank outlet, the risk is Unporting both outlets at once and that can be easily done if you are feeding off one tank and out of balance. The wing has a 1 degree dihedral so if you are out of balance/slipping you can have plenty of fuel in the far end of the tank and lots of air in the outlets. Running on both will mitigate this risk only until you empty the other tank.

2 People have different preferences of operation for different reasons, nothing wrong with that. What is essential is an understanding of the system and the factors affecting it. There are compelling arguments for burning tanks out and knowing what you’ve got left or for running on both, and knowing what you’ve got left.

3 If your ball isn’t in the middle your gauges won’t read accurately and if you’re on both you can end up with a serious fuel imbalance. We know from experience that if you lose a fuel cap the fuel escapes from that wing and the low pressure drags fuel across from the good tank. This is yet another reason for good pilot discipline in regularly checking your gauges!

I used to fly an aircraft that required a set of vice grips to be carried as the type was prone to the fuel selector handle breaking as you switched tanks. Also due to the position of the selector in the B model and my Orangutan gene not being quite strong enough it’s really not that comfortable for me to reach my fuel selector in flight, definitely doable just not enjoyable. So for these reasons the only time I touch my fuel selector is when I’m parked on a slope to stop X feeding. That doesn’t mean that if I’m going to operate close to my fuel margins I won’t choose to burn a tank out, I may depending on the circumstances.

I agonised over going from carbureted to injected due to potential fuel system issues, particularly Unporting, pump requirement etc, I got over all of that with testing and am now happy with that choice. But what I would say is that if you are thinking you can let your engine stop and switch tanks be cautious with respect to speed and height and with composite low inertia props. When my first engine failed on final I was shocked at how quickly the prop stopped turning.

**Nev** · 11-29-2022, 11:44 PM

Originally posted by Battson View Post

I want to reiterate that there have been several near misses and at least one fatality in Bearhawk aircraft due to apparent mismanagement of the fuel system and / or not flying in balance, apparently causing a tank to unport

Do you mind me asking what was the accident due to fuel mismanagement / not flying in balance ? I don't think I was aware of this.

**jaredyates** · 11-30-2022, 12:04 PM

Something that I'd propose: how about if someone writes up a nice Beartracks article that sums up all of the nuance to this?

**Nev** · 11-30-2022, 12:29 PM

Originally posted by jaredyates View Post

Something that I'd propose: how about if someone writes up a nice Beartracks article that sums up all of the nuance to this?

Welcome to use THIS one or any of the articles on the website Jared, They're all aimed at helping new Bearhawk pilots avoid the issues myself and others experienced..

(They're not there to persuade the more experienced guys to change their SOP's.)

**whee** · 11-30-2022, 01:05 PM

Originally posted by jaredyates View Post

Something that I'd propose: how about if someone writes up a nice Beartracks article that sums up all of the nuance to this?

The problem I see with this idea is that no one fully understands all the nuances, ie no one is qualified. You’d have a flawed summary. But as long as that summary aligns with the BH think tank then I suppose all will be fine.

Personally, and I think this plays a role in why people leave the group after finishing their builds, I find it disheartening when an experience is shared that may show an area of the BH that could possibly be improved but the builder/pilot gets the finger pointed back at them. Life is too busy, time to too precious to spend much effort in dialogue with folks who’ve already made up their minds.

**schu** · 11-30-2022, 02:00 PM

Originally posted by jaredyates View Post

Something that I'd propose: how about if someone writes up a nice Beartracks article that sums up all of the nuance to this?

Originally posted by whee

The problem I see with this idea is that no one fully understands all the nuances, ie no one is qualified. You’d have a flawed summary.

I already wrote a summary: It's post 16.

https://bearhawkforums.com/forum/saf...9404#post59404

I'm firmly in the camp of explaining the nuance and educating people. Bob's Operational notice says to install a header tank if you have a pump, but I think that ignores nuance as an EFI system moves WAY more fuel than a return-less mechanical system. It also ignores the nuance of building and installing a header tank.

So many times in this thread people mention that their system is injected and uses the stock fuel system and is validated to be safe, but rarely do they define specifically which injection they have. I'm worried that a new builder would decide on EFII or SDS electronic fuel injection and not understand that the safety of their aircraft absolutely depends on gravity supplying fuel to the pump faster than it can pump it, which is much faster than the total fuel consumption at wide open throttle.

As for uncoordinated flying. This is the thing Nev brings up a lot, but I don't find that to be a fuel thing as much as a flying the airplane well thing. If you fly the airplane poorly then you probably want to self impose a lot of limitations: Don't use more than 1/2 tank of fuel, don't use the last 1/2 of the CG, don't land on anything less than 3000', don't fly at night, don't fly in the mountains, don't fly when there is more than a 2kt crosswind, etc....

In summary, if you are new to bearhawks and you don't know what to do then pick one:

1. Build with a carb, use the factory fuel design, and fly the airplane well.
2. Build with a returnless mechanical injection system like bendix or airflow, use the factory fuel system design with a boost pump and engine pump, and fly the airplane well.
3. Become a test pilot, thoroughly educate yourself on how systems fail, do what you want, test the hell out of it, and fly the airplane well.

**Nev** · 11-30-2022, 03:39 PM

Originally posted by schu View Post

As for uncoordinated flying. This is the thing Nev brings up a lot, but I don't find that to be a fuel thing as much as a flying the airplane well thing. If you fly the airplane poorly then you probably want to self impose a lot of limitations

Yes I do go a bit

.

I enjoyed reading your observations on the previous post Schu, some excellent insights. I think you're spot on actually about being able to fly the plane properly. But I do think alot of people will initially struggle with the Bearhawks very sensitive rudder. It was something I didn't fully comprehend until mine was finished and flying, even though it's been commented on alot in various forum posts over the years. After 175 hours in my Bearhawk and 750 landings, it requires my constant attention, and nearly every pilot that I've taken for a ride has mentioned it to me.

My observation is that this has a direct effect on the fuel system operation.

**schu** · 11-30-2022, 05:19 PM

Originally posted by Nev View Post

Yes I do go a bit

.

I enjoyed reading your observations on the previous post Schu, some excellent insights. I think you're spot on actually about being able to fly the plane properly. But I do think alot of people will initially struggle with the Bearhawks very sensitive rudder. It was something I didn't fully comprehend until mine was finished and flying, even though it's been commented on alot in various forum posts over the years. After 175 hours in my Bearhawk and 750 landings, it requires my constant attention, and nearly every pilot that I've taken for a ride has mentioned it to me.

My observation is that this has a direct effect on the fuel system operation.

I agree that the design is shorter and has more rudder to vertical stab ratio than I prefer, making it more sensitive to yaw as well as having less yaw stability compared to other designs. If you look at a 185 about 1/3 of the vertical is rudder and 2/3 stab, while the bearhawk is probably 1/2:1/2 like a cub or pacer.

There are things you can do about it, like stiffer rudder springs, or perhaps a ventral fin like the float guys use, but once you get used to it, your brain does the right thing so no big deal.

My 170A also does things that people don't like, such as adverse yaw, and it's pronounced enough you end up using opposite aileron to cancel additional roll while in a turn. It is what it is.

My solution to all of this is really simple. Get really good at flying the airplane, and for the times where I'm doing long cross countries and want to relax: 3 axis autopilot.

schu

**kestrel** · 12-01-2022, 09:50 AM

Originally posted by Nev View Post

alot of people will initially struggle with the Bearhawks very sensitive rudder.

That is an interesting characterization. I've seen that many first timers have issues with the adverse yaw but they sort it out reasonably quickly. Aileron movement requires rudder movement with it. I've never noticed the Bearhawk yawing or dutch rolling in turbulence. It seems sufficiently stable on the yaw axis. (...as well as on the others)

One of things that I love about the Bearhawk is the amount of rudder authority. This is very useful for crosswinds. However, the first time that I came over a tall set of trees and kicked to rudder to slip it, the yawing motion really caught my attention!

**Nev** · 12-01-2022, 01:29 PM

Some pilots have much greater experience with short coupled similar type aircraft, so will be very good at flying the Bearhawk right from the start. (I wasn't one of them).

It would be interesting to compare the propeller arm from the Datum of a few of our Bearhawks. The longer the prop arm, the more engine cowling area, and probably the less stable in yaw. I know Mark has commented on this before in the forum and said that Bob didn't recommend adding a longer prop spacer. I don't know this to definitely be a factor, but it could explain why some Bearhawks are more sensitive in yaw through built variation.

In this post HERE you can see 3 different prop arm lengths and engine cowling area. Bobs original aircraft would have been significantly more stable on the yaw axis.

**Battson** · 12-01-2022, 05:31 PM

Originally posted by kestrel View Post

I entirely agree with all three of these statements.

The problem I'm having is that more than one of your posts state that any conclusion other than yours is wrong.

Well, obviously that's not what I said. I've said I think it adds risk and that I don't see clear benefits.

If someone wants to explain how changing tanks regularly lowers the risk and offers advantages, compared to using both tanks most of the time, (using a clear substantive argument) that would be helpful.

Originally posted by kestrel View Post

I conclude from all of this that either strategy can work well if you have tested and are paying attention to the systems. If you have not tested or are not paying attention, either strategy can get you into trouble. The fuel selection strategy is essentially a red herring.

Totally agree with the first half of your conclusion, there are many workable strategies. The point was, I don't believe all are identical in terms of risk / benefit.

A "red herring"? While it appears to be an esoteric issue, Bearhawk pilots are having nasty experiences because of fuel system management; so we're discussing it.

If the pilot can't fly the plane straight and doesn't monitor fuel quantity, then I agree - they can run out of fuel earlier than they expected... but I mean... c'mon

Those are two very separate issues!

Aviation safety fundamentals - fly the plane, monitor fuel quantity. I don't accept that those are downsides of flying on 'both tanks'. We need to deal with those issues separately, and in the meantime the pilot might want fuller tanks. Selecting the fullest tank is no good, if you can't fly in balance.

Announcement

Operation Notice from Bob about Fuel Tanks on Systems with Fuel Pumps

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