Problem solved: High CHT on #3 Cylinder
Great recommendation!
Gust Kalatzes
Active Member
You can make that piece cheap! Do a baffle search and find Tom D's pattern with dimensions on it and make one. I have it and will try to find it.
If you are having temp problems on all the cylinders extend all the baffling and fill all the holes. It's not difficult but takes about a day, or two, if you add the silicon dam's on the back of the nose bowl. The #3 baffle mod will fix number 3 but not the others without extending and properly sealing the baffle.
Another way to fix #3, if you are good with metal, is you could gently hammer a valley out in the baffle behind #3 that contacts the casting line. If the rest of the baffle is fixed you can get by with a 1/8' gap behind the casting line. I made 3 or 4 cheezy vids on youtube under "gustlock57" if interested.
If you are having temp problems on all the cylinders extend all the baffling and fill all the holes. It's not difficult but takes about a day, or two, if you add the silicon dam's on the back of the nose bowl. The #3 baffle mod will fix number 3 but not the others without extending and properly sealing the baffle.
Another way to fix #3, if you are good with metal, is you could gently hammer a valley out in the baffle behind #3 that contacts the casting line. If the rest of the baffle is fixed you can get by with a 1/8' gap behind the casting line. I made 3 or 4 cheezy vids on youtube under "gustlock57" if interested.
TheFlyingMouse
Active Member
I sent an email and also got similar pricing very recently so it isn’t just you, unfortunately.
I’m debating. Cylinder #4 is actually my hottest. It’s probably worth going through with a fine tooth comb on gaps anyway so I’ll probably do that first and see if the Aviat pricing is just a temporary supply issue.
I know the front baffle seals don’t quite contact the front cowling and the last tweak on this helped a lot, so I’ll start there and work my way to smaller holes.
Snowbirdxx
Well-Known Member
I posted the plan for the cup here in the beginning of this thread. , you can make it from a beer can. Half an hr work, once the baffle is out. To get it out, loosen all the bolts and then hook an electric drill to the frontend of the interconnect rod, while holding the nut in the back.
Gentlemen,
Nobody can make anything for less than $10 these days. You can't even buy lunch at McDonald's for $10 now. When I had a B model I purchased all of these parts and they worked. I didn't pay $1100 but those parts were still expensive (especially if $10 is the expectation). All Aviat parts (and aircraft) are made by hand and that's expensive.
I could have made them myself if I spent a week prototyping parts out of cardboard, then spending $100-$200 on supplies, and finally bending and drilling aluminum. If I'm lucky the 2nd or 3rd attempts would be usable. Voila!! I just burned $2500 worth of my time, spent over $100 on raw materials, had my aircraft torn down for a week, and ended up with amateur built parts that may or may not work as well as the $1100 Aviat parts. Not exactly saving big. Thanks but I'll stick with the Aviat parts.
I know expensive parts are frustrating brother but trust me when I say that's far less frustrating than parts that aren't available at any price. I'm a car collector as well and old Porsche parts are really expensive but to their credit Porsche continues to support ALL of their street cars, even those 50+ years old by continually reproducing parts and keeping them available. Aviat does the same thing. Compare that to to my 17 year old Ford GT where most of the parts aren't available at ANY price. Many GT's sit for months while owners search for parts out of wrecked GT's.
Aviat will not be closing their doors. They survive hand building just 24 aircraft a year and supporting the existing fleet with parts and service with 55 employees. As a business owner I can assure you that's not an easy gig and I for one am thankful they do it. Every pilot who loves Husky's should be thankful as well. They aren't killing a fat hog doing that.
We've all watched the price of Lycoming engines we use to buy for $20,000 climb to over $100,000. Very limited production and hand building makes things expensive. But that's still a bargain compared to unavailable. That's my take on it.
Chip
Last edited:
Chip,
Your response reminds me of folks rationalizing a $30 charge for an aspirin from a hospital ER.
10 dollars for material at their cost for twelve rivets and around 30 square inches of aluminum for parts that would correct the design flaw that Aviat itself was responsible for is not ridiculous. I know that some folks think that Aviat's design solution of a complete new rear baffle is the solution; however, any competent sheet metal worker could inspect the baffle once removed and look at Lycoming's cylinder head to make the flow blister parts similar to Thomas D.'s sketch in less than an hour, first try without a drawing.
It obvious that you think that the owners of the original flawed baffle design should be paid twice, once for the original flawed design and again to fix the design problem. I don't! Aviat could have easily generate a Service Bulletin with a sketch to fix the problem that any repair shop could blindly handle, but they didn't. Instead they came up with a $1,100 solution. In no way do I believe that Aviat's design/pricing approach was or is conducive to bringing more folks into general aviation.
So what should a $10 dollar part retail for? 5 times the parts at cost, $50 for the sub assembly parts?? Or $1,100 for the complete assembly to fix the problem.
groshel
Active Member
I started my career in Grumman American’s light aircraft production…started as an assembler and four years later Flight Line Inspection then on to Gulfstream production and service engineering.
Dogday is more right than Chip in my opinion.
Yes, they do have to amortize Engineering / drawings, prototyping and tooling costs..maybe even some flight testing. For a small efficient factory that should be quick and easy ….when they start fabricating the assemblies it should go quickly even when building say 50 shipsets. And I don’t imagine Afton is a high wage area either.
And yes, it is a fix for their screw-up…but that hadn’t stopped my old employer and others from hitting up customers for the big bucks for minor fixes. Unfortunately it seems to be some manufacturers style..I don’t ever see anyone giving things away for free or even cheap.
I do feel $1100 is excessive and so is the lead time considering they probably use it in current models and should have some on hand. If they aren’t building multiples at one time for a design that doesn’t change they have production planning issues.
I just ordered two lower aileron skins from K&L Soaring…the remnants of the old Schweizer Aircraft. Several bends on a 48” by 8” piece of aluminum that’s alodined. $110 each….for an aircraft that had a 600 aircraft production run and a company that is now much smaller than Aviat. That’s a deal!
Chris
Dogday is more right than Chip in my opinion.
Yes, they do have to amortize Engineering / drawings, prototyping and tooling costs..maybe even some flight testing. For a small efficient factory that should be quick and easy ….when they start fabricating the assemblies it should go quickly even when building say 50 shipsets. And I don’t imagine Afton is a high wage area either.
And yes, it is a fix for their screw-up…but that hadn’t stopped my old employer and others from hitting up customers for the big bucks for minor fixes. Unfortunately it seems to be some manufacturers style..I don’t ever see anyone giving things away for free or even cheap.
I do feel $1100 is excessive and so is the lead time considering they probably use it in current models and should have some on hand. If they aren’t building multiples at one time for a design that doesn’t change they have production planning issues.
I just ordered two lower aileron skins from K&L Soaring…the remnants of the old Schweizer Aircraft. Several bends on a 48” by 8” piece of aluminum that’s alodined. $110 each….for an aircraft that had a 600 aircraft production run and a company that is now much smaller than Aviat. That’s a deal!
Chris
Oryx
Active Member
I think you all make good points. And I think it really comes down to the companies values and how those are played out in customer service.
I’m really glad Aviat acknowledged there was a problem (all be it decades later) by producing a fix for the nearly universal issue. It also seems to be quite simple.
Supporting the used Husky owners market must be pretty tricky considering it includes planes ranging in price from $50-$500 thousand and owners that are equally diverse.
But, it would be amazing if they really supported the previous sold planes with free item like dash placards (stickers), flaw fixes like this baffle item, sliding window seals, and a hat or T-shirts. The total cost to the company would be peanuts compared to the advertising and promotion budget and it seems it would create really loyal and bragging-type of Husky owners.
At any rate we’re fortunate to be able to fly these planes and it’s really none of our business how they run there’s.
I’m really glad Aviat acknowledged there was a problem (all be it decades later) by producing a fix for the nearly universal issue. It also seems to be quite simple.
Supporting the used Husky owners market must be pretty tricky considering it includes planes ranging in price from $50-$500 thousand and owners that are equally diverse.
But, it would be amazing if they really supported the previous sold planes with free item like dash placards (stickers), flaw fixes like this baffle item, sliding window seals, and a hat or T-shirts. The total cost to the company would be peanuts compared to the advertising and promotion budget and it seems it would create really loyal and bragging-type of Husky owners.
At any rate we’re fortunate to be able to fly these planes and it’s really none of our business how they run there’s.
TheFlyingMouse
Active Member
To me the issue is the sudden increase in price we’ve observed. I looked through the forum history when I emailed Aviat. Before Covid, I believe Kent got one for under 400. Someone else got one for a bit over 500 just a year ago. Now it’s suddenly 1100. I understand there’s been a lot of inflation, but this is excessive.
The thing that really bothers me is these costs seem to be accelerating. The prospect of shelling out $100k for a new O-360 that Chip just wrote about is alarming. I had eyeballed the price for a new engine to be around 50k a few years ago and assumed it would increase roughly with common inflation. If I had “officially” set the engine replacement money aside in the S&P500 at the time, I don’t think it would have kept up. That’s pretty crazy.
I guess this has been the state of GA as a whole for a while now, but it’s indicative of the trend continuing rather than getting better.
The thing that really bothers me is these costs seem to be accelerating. The prospect of shelling out $100k for a new O-360 that Chip just wrote about is alarming. I had eyeballed the price for a new engine to be around 50k a few years ago and assumed it would increase roughly with common inflation. If I had “officially” set the engine replacement money aside in the S&P500 at the time, I don’t think it would have kept up. That’s pretty crazy.
I guess this has been the state of GA as a whole for a while now, but it’s indicative of the trend continuing rather than getting better.
There is another cost factor besides parts, labor and testing. That is the certification cost of making sure this is an approved part which extends long after testing is complete. I am currently working on two different airboxes for different aircraft and trying to add them to existing STCs. Simple sheet metal and fasteners with a little welding. Extremely simple parts to replace extremely simple parts. Both are going on 8 months after testing was complete for FAA approval. Hours per month on the phone, exchanging emails, paying additional DERs to help cut through additional red tape after all approved testing was completed months ago . . . just to get the project handed off to a different manager and start it all over again with somebody who has no idea what was done for the previous 12 months. These are parts which sat in inventory through tax season. By the time $150 worth of materials and welding can legally be put on an airplane I find it very easy to believe that $1000 each will take 100 sales for me break even. Instead we will probably increase the cost of all of our other parts minimally and drive the price of this into the overall budget. Only people who have been through the STC process from start to finish can truly appreciate the reality of this struggle.
As for this specific piece of baffle on the Husky, I have no insider knowledge on what it took for Aviat to get it to market. Having been through this process several times I find it very easy to believe the folks at Aviat had this designed, tested and on the shelf in stock 4+ years ago. Their project manager at the FAA asks why they want to make the change. Aviat informs them that it fixes a widely known cooling issue. The FAA pounces on the chance to conduct an investigation into a known issue!!! Years later Aviat finally has approval and can sell the dusty parts on the shelf. I am not saying this IS what happened, but in my experience it is at least as likely as them simply trying to stick it to their existing customers to make a few hundred bucks extra.
I am fairly new to this forum so there may be some history that I am not aware of that would cast doubt on my hypothetical timeline. Just relating my experience getting what is a simple piece of sheet metal turned into an approved, airworthy part.
Cheers,
Ian
As for this specific piece of baffle on the Husky, I have no insider knowledge on what it took for Aviat to get it to market. Having been through this process several times I find it very easy to believe the folks at Aviat had this designed, tested and on the shelf in stock 4+ years ago. Their project manager at the FAA asks why they want to make the change. Aviat informs them that it fixes a widely known cooling issue. The FAA pounces on the chance to conduct an investigation into a known issue!!! Years later Aviat finally has approval and can sell the dusty parts on the shelf. I am not saying this IS what happened, but in my experience it is at least as likely as them simply trying to stick it to their existing customers to make a few hundred bucks extra.
I am fairly new to this forum so there may be some history that I am not aware of that would cast doubt on my hypothetical timeline. Just relating my experience getting what is a simple piece of sheet metal turned into an approved, airworthy part.
Cheers,
Ian
TheFlyingMouse
Active Member
Ian,
I think that’s very useful insight, although it still leaves me scratching my head about significant price jumps for already sold-to-others parts in this case. The only guess I could have there is Aviat must have overestimated how many they would sell and has decided to true up.
I completely agree that the bureaucratic monster is what is killing general aviation, and the situation sucks for everybody and it’s not fair to assume mal-intent on the part of the businesses. It doesn’t change the fact that these costs are getting out of hand. One by one, more of us will have to drop out when faced with the hard math, and that’s going to put a lot of companies out of business in the end too. I doubt even Chip here would be willing to cough up $10k (in today’s dollars) for something like this part without giving somebody a funny look first. Everyone has their limits.
I guess the answer is we need to (as a community) get the FAA to relax some of the rules around more minor parts for certified aircraft like they’re doing for LSA restrictions right now.
I think that’s very useful insight, although it still leaves me scratching my head about significant price jumps for already sold-to-others parts in this case. The only guess I could have there is Aviat must have overestimated how many they would sell and has decided to true up.
I completely agree that the bureaucratic monster is what is killing general aviation, and the situation sucks for everybody and it’s not fair to assume mal-intent on the part of the businesses. It doesn’t change the fact that these costs are getting out of hand. One by one, more of us will have to drop out when faced with the hard math, and that’s going to put a lot of companies out of business in the end too. I doubt even Chip here would be willing to cough up $10k (in today’s dollars) for something like this part without giving somebody a funny look first. Everyone has their limits.
I guess the answer is we need to (as a community) get the FAA to relax some of the rules around more minor parts for certified aircraft like they’re doing for LSA restrictions right now.
Personally, I don't see "relaxing the rules" will be all that effective. At least not the testing rules. While testing is painfully expensive most (certainly not all) of it exists for a specific reason that ensures safety in one way or another. Expensive tests make for expensive products and that is simply the nature of airplanes if we want them safe. There are certainly some tests that need to be reviewed in light of new methods being possible due to new technology but that is a very minor thing compared to the red tape/bureaucracy problem. The way I see it, this is currently a two headed monster.
The first portion of this is a combination of internal policies that conflict with one another and/or the FARs. For instance, an FAR may say that DERs can sign of minor changes X,Y & Z. A new internal policy says changes X & Y must always be reviewed by the FSDO manager to be approved. The DER following the regulations signs off on a minor sheet metal change like this baffle piece. Two years later a FSDO manager hears about it and starts an investigation and grounds hundreds of planes based on internal policy documents that the DER has never seen or heard of but is required to comply with in conflict with published regulations. The investigation moves at the speed of government. This type of problem is rampant.
The second problem is a personnel issue that plagues all large companies and agencies but is particularly troublesome in an industry which requires a great deal of technical knowledge. That is the % of people in positions of power that have the required technical knowledge. There are a lot of good, very knowledgeable and capable people in the FAA. There are also a lot of people who got a good government job with a pension and are happy doing paperwork at a desk until retirement, but their aviation knowledge is limited to a 50% success rate distinguishing the difference between a bird and a plane when in flight. The problem arises when one of the latter group's signature is required and they are reluctant to sign off because they don't understand what is in front of them.
Examples, I was once instructed to hire an electrical DER to make a report that explained why no electrical DER was needed for parts that included no electrical components, nor interacted with any electric systems. Do I spend the money and time to comply just to cut the red tape or do I spend the time and money attempting to justify why it is not needed, to somebody who clearly doesn't understand the difference between a hose and a wire? Another time I was told an airframe DER was required. There are lots of electrical DERs and structural DERs and the list goes on . . . but there is no such thing as an "airframe DER". Time and money spent trying to get somebody to explain what they don't understand so I can figure out which combination of expensive consultants they think they may have intended to mean. You could be lucky enough to get an all FAA rockstar team on your project just to have one person (and you often end up with more than one) halt the progress of the entire team for years with no recourse. Eventually you may get to the point where these delays can only be explained as intentional and figure out who their boss is, or their boss. Calling them will very likely make an enemy of the person causing additional the delays. Having enemies inside the FAA is never a good idea. What to do? These may seem like fairly trivial hurdles to move past but our first STC took eight years in the formal process. The first four years was a lot of learning the process and many of those delays are on us but we finally got all of the required testing done and the final paperwork submitted. It took four more years of waiting for the final STC to be issued. Four years of paying a lease on a hangar, all the phone/electric/water/website/etc. expenses of running what should already be a solvent business, keeping the plane airworthy while waiting for our first product to be legal to sell. All costs that must be pushed to the customer or the business fails. Second STC took 18 months from the time the plane rolled into the hangar to tests completed. Two more years before it was issued. Our most recent STC took about 12 months to all testing completed, then four years with no changes waiting for the STC to be issued.
I didn't intend this to be so long, but as I see it loosening the rules won't help. It is these inexcusable and unreasonable delays that drive most of the excess cost that must be passed on to the customer. Reviewing the rules and deleting half of them that conflict with one another is the first step. Then some sort of formal process to report the unconscionable behavior and . . . this is the important part . . . a path to resolution which will be adhered to. Not just lead to another delay caused by somebody who's pride was hurt or a third person who sits on it again for whatever reason. The FAA is vital to the health of the aviation community from casual pilots to aircraft manufactures and all the smaller STC holders and commercial operations in-between. We all strive to stay in their good graces every day to ensure safe skies. I have no problem complying with every rule they put in front of me. It is the rules that are designed so they can not be complied with, which have no possible solution except to sit around waiting for years for a signature that vex me and pass indefensible expenses on to you.
Cheers,
Ian
Dogday,
I’m not rationalizing anything, I’m pointing out a few erroneous assumptions. Example: “correcting a design flaw that Aviat itself is responsible for”. Aviat didn’t even exist when the Husky was designed by Herb Anderson and his team for Christen Industries. Aviat didn’t exist when the first 400 Husky’s were built with that design (that was certified and approved by the FAA). Stuart Horn is the 2nd owner of Aviat. He bought a factory and the right to continue production of an FAA previously certified aircraft. Almost any change in that design requires a lengthy and expensive approval process.
My first Husky, a 1992 A-1, is still flying just fine today (along with about 1000 other Husky’s) with those original baffles, so clearly they are adequate. Not optimal, but adequate. I didn’t know back then that the cylinder head temps varied a lot as there was only a temp probe on the hottest cylinder. I flew it a lot, loved the plane, and it worked. The original engine went beyond its 2000 hour TBO. Husky’s aren’t falling out of the sky because of those original baffles and it’s not a safety issue. It’s an original design that “could be better”.
There are a lot of parts and design components on every aircraft/car/boat that could be better. When serious safety issues are involved a recall might be employed or the FAA will issue an AD. None of that is in play here. On my 2nd Husky I had temp info on all 4 cylinders and could see they weren’t even and don’t we all want those as even as possible? I also didn’t think the original aileron design with the spades and that damn bungee trim system was optimal but those items didn't keep me from buying a Husky.
But I didn’t expect Stuart Horn and the current company making 24 aircraft a year to continually design an make available (for $10) non safety related design improvements for the entire fleet of over 1450 aircraft, a large percentage of which were not even made by my company and are a decade or more out of warranty. I think that’s unrealistic.
It would be nice if the warranties on products I buy never expired and I was entitled to free or below cost fixes and improvements forever. But the truth is that once my warranty expires on any vehicle, barring a recall or a safety issue or AD, I’m not entitled to anything.
We both agree that if those parts were free or super cheap that would be great. It would be nice if the $69,000 price of my first brand new Husky was still available today (over $500,000 now). But that’s not the case. I won’t be so presumptuous as to say “it’s obvious that you think….” but it’s safe to say I believe I’m entitled to a lot less than you do. That’s all.
Chip
Last edited:
TheFlyingMouse
Active Member
Well, summer’s here and I should finally be able to go fly this weekend after 3 weeks’ hiatus. Cowl’s got to come off for an oil change so I think I’ll finally spend some quality time with a tube of red silicon and get a look at what’s involved with all of these baffle mods.
I figure if I place an order, I should get the #3 baffle and the two deflector ones at the same time. I think that’s the following part numbers?
35380-504
354280-05
354280-06
I’d jump the gun on the cooling lip too, but this is liable to be hard enough to explain to Mrs. Mouse for the time being, and I don’t think any of these require cutting on the cowling.
I assume silicon must always be applied on the high pressure side of any gap to be of value? (Excepting the nose bowl mod).
I figure if I place an order, I should get the #3 baffle and the two deflector ones at the same time. I think that’s the following part numbers?
35380-504
354280-05
354280-06
I’d jump the gun on the cooling lip too, but this is liable to be hard enough to explain to Mrs. Mouse for the time being, and I don’t think any of these require cutting on the cowling.
I assume silicon must always be applied on the high pressure side of any gap to be of value? (Excepting the nose bowl mod).
Not necessarily. If the surfaces it is bonding to are fairly clean, makes enough contact, and the gap is fairly narrow it will hold from either side.
Highroad
New Member
I have not done anything yet with my baffle situation and high #3 cylinder head temps. We were flying the Idaho and Oregon backcountry last week, and these are a few of the things I noticed. The OAT's across the west were high last week, so I was nervous about what my engine temps would be.
In short, I'm trying to figure out if I have a fuel distribution issue (carburated O-360 in a 98' A1-A) or if the hot cylinder's have higher egt's because they are hotter, if that makes sense?
Here are some things that I noticed. I have a CGR 30 engine monitor and Surefly Electronic ignition on one mag.
Also, I live on the Oregon coast, so I often take off at sea level in sub 70 degree coastal temps and climb to 9-11K ft to fly the 400nm to Idaho. OAT's last week in the 9-10K ft range were 50-60 degrees (cruise). When we get to Idaho, the departures happen from 3500-7000ft and the climb may be short to clear terrain into the next drainage, etc. OAT's on the ground were sometimes 80-85 degrees last week, so the DA was high/hot. All this being said, the temps seem to behave as described below:
Cylinders 1 and 2 never got above 350 or so in climb, and in cruise they are in the low 300's and even high 200's
Cylinder 3 goes above 400 degrees almost immediately after takeoff power is applied and I regularly saw 425 degrees during climb. I was climbing at full throttle and 2500 rpm, and trying to keep #3 egt around 1250 degrees with fuel flow. It hovers right around 400 degrees in cruise at 20-21'' manifold pressure and 50-75 degrees rich of peak
Cylinder 4 will get to 400 degrees in a sustained climb, but then settles in around 370 or so in cruise. Outside air temps were 80 degrees or so in the climb and 60 degrees or so in cruise at altitude.
The EGT spread is pretty wide, almost 100 degrees. The cooler cylinders have the lower egt. I realize this airplane is carbureted, but is it possible the hot cylinders are not getting enough fuel, or is the higher egt due to the higher cylinder head temp?
When I lean the engine, even at low power settings (19-20''), it seems like I have to give it more fuel than is needed to keep the #3 cylinder at 50 degrees ROP. The rest of the egt's seem pretty rich compared to #3
Is it possible that the rear cylinders are not getting the fuel they need somehow, or the front cylinders are getting to much?
Or, is this just a baffle issue and if I can get more air to #3 and maybe even #4, my egt spread will be more reasonable?
Brent
In short, I'm trying to figure out if I have a fuel distribution issue (carburated O-360 in a 98' A1-A) or if the hot cylinder's have higher egt's because they are hotter, if that makes sense?
Here are some things that I noticed. I have a CGR 30 engine monitor and Surefly Electronic ignition on one mag.
Also, I live on the Oregon coast, so I often take off at sea level in sub 70 degree coastal temps and climb to 9-11K ft to fly the 400nm to Idaho. OAT's last week in the 9-10K ft range were 50-60 degrees (cruise). When we get to Idaho, the departures happen from 3500-7000ft and the climb may be short to clear terrain into the next drainage, etc. OAT's on the ground were sometimes 80-85 degrees last week, so the DA was high/hot. All this being said, the temps seem to behave as described below:
Cylinders 1 and 2 never got above 350 or so in climb, and in cruise they are in the low 300's and even high 200's
Cylinder 3 goes above 400 degrees almost immediately after takeoff power is applied and I regularly saw 425 degrees during climb. I was climbing at full throttle and 2500 rpm, and trying to keep #3 egt around 1250 degrees with fuel flow. It hovers right around 400 degrees in cruise at 20-21'' manifold pressure and 50-75 degrees rich of peak
Cylinder 4 will get to 400 degrees in a sustained climb, but then settles in around 370 or so in cruise. Outside air temps were 80 degrees or so in the climb and 60 degrees or so in cruise at altitude.
The EGT spread is pretty wide, almost 100 degrees. The cooler cylinders have the lower egt. I realize this airplane is carbureted, but is it possible the hot cylinders are not getting enough fuel, or is the higher egt due to the higher cylinder head temp?
When I lean the engine, even at low power settings (19-20''), it seems like I have to give it more fuel than is needed to keep the #3 cylinder at 50 degrees ROP. The rest of the egt's seem pretty rich compared to #3
Is it possible that the rear cylinders are not getting the fuel they need somehow, or the front cylinders are getting to much?
Or, is this just a baffle issue and if I can get more air to #3 and maybe even #4, my egt spread will be more reasonable?
Brent
belloypilot
Active Member
What I’ve discovered in experimenting with mixture and power settings in my 1999 A-1B is the distribution of fuel/air ratios across cylinders seems to change with throttle butterfly position and, to a lesser extent, with induction air temperature. Throttle positions at or near wide open seem to provide less of a spread across cylinders in terms of the fuel flow at which each EGT reaches peak. Partial carb heat also seems to even things out a bit. I’m not advocating any particular throttle or carb heat setting, just pointing out my observation of what seems to even out fuel/air ratios.
When leaning, the cylinder(s) that peak first are getting either less fuel or more air and vice versa for those that peak last. I have seen that cylinders 3 and 4 run slightly leaner, but if your leanest cylinder is 50 degrees or more ROP and there’s still a significant CHT spread, I don’t think the high CHT issue is primarily mixture related. It’s more likely a cooling issue. As I’ve mentioned earlier in this thread, I have the Aviat front blocking baffles, the Aviat #3 baffle modification, and the Thomas Dietrich lower cowl cooling lip and the combination has resulted in CHTs under 400 on warm day, Vy climbs, and usually a 20 degree temperature spread in cruise. The #3 baffle mod was the last thing I did, and the most effective.
My $0.02
Cheers.
When leaning, the cylinder(s) that peak first are getting either less fuel or more air and vice versa for those that peak last. I have seen that cylinders 3 and 4 run slightly leaner, but if your leanest cylinder is 50 degrees or more ROP and there’s still a significant CHT spread, I don’t think the high CHT issue is primarily mixture related. It’s more likely a cooling issue. As I’ve mentioned earlier in this thread, I have the Aviat front blocking baffles, the Aviat #3 baffle modification, and the Thomas Dietrich lower cowl cooling lip and the combination has resulted in CHTs under 400 on warm day, Vy climbs, and usually a 20 degree temperature spread in cruise. The #3 baffle mod was the last thing I did, and the most effective.
My $0.02
Cheers.
Highroad
New Member
Mike, thank you for your thoughts on this. I was thinking I should of pulled in some carb heat to see if it would even out the temps some. Will experiment with this some as I'm curious.
I need to do the #3 baffle mod, as I think this is ultimately the issue.