Cherokee getting fat

[[email protected]]

We finally did it.... we had to weigh the airplane. After three years of
owning it, upgrading radios, adding whatzits (Tannis heater, vacuum filter, new
strobe, etc), we finally had a custom interior made up for it. Since the last
weighing was without an interior and the weight/moment would be hard to compute, we
figured putting it on the scales would be a good plan.

Old calculated weight: 1307
New measured weight: 1379

A few gotchas...The measured weight was without fuel, but with 6 qts of oil.
The calculated weight should have included everything except wheel pants and the
interior that had been installed. I was figuring about 30 lbs for the interior, and
10 for the pants, but that's still 25 lbs heavior than it should be.

Sound about normal for those who've done the same? Without having to take
them off, anyone know what wheelpants for a Hershey-bar cherokee weigh/balance?

Maybe *I* need to go on a crash diet before the big AK trip... :)
-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Margy]

wrote:
> We finally did it.... we had to weigh the airplane. After three years of
> owning it, upgrading radios, adding whatzits (Tannis heater, vacuum filter, new
> strobe, etc), we finally had a custom interior made up for it. Since the last
> weighing was without an interior and the weight/moment would be hard to compute, we
> figured putting it on the scales would be a good plan.
>
> Old calculated weight: 1307
> New measured weight: 1379
>
> A few gotchas...The measured weight was without fuel, but with 6 qts of oil.
> The calculated weight should have included everything except wheel pants and the
> interior that had been installed. I was figuring about 30 lbs for the interior, and
> 10 for the pants, but that's still 25 lbs heavior than it should be.
>
> Sound about normal for those who've done the same? Without having to take
> them off, anyone know what wheelpants for a Hershey-bar cherokee weigh/balance?
>
> Maybe *I* need to go on a crash diet before the big AK trip... :)
> -Cory
>

I did some recent calculations for an upcoming trip via helicopter we
are taking in Australia with friends. Total allowed weight = 700 lbs
Total combined weight for the 4 of us = 638 lbs Total weight lost by all
of us since Christmas break = 90 lbs. I'm really glad the diets worked!!

Margy

[Jay Honeck]

> I did some recent calculations for an upcoming trip via helicopter we are
> taking in Australia with friends. Total allowed weight = 700 lbs
> Total combined weight for the 4 of us = 638 lbs Total weight lost by all
> of us since Christmas break = 90 lbs. I'm really glad the diets worked!!

I *thought* you guys looked thin(ner), but never had the chance to say
anything. Good job!

90 pounds -- wow!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Nathan Young]

On Mon, 20 Jun 2005 11:40:41 +0000 (UTC),
wrote:

> We finally did it.... we had to weigh the airplane. After three years of
>owning it, upgrading radios, adding whatzits (Tannis heater, vacuum filter, new
>strobe, etc), we finally had a custom interior made up for it. Since the last
>weighing was without an interior and the weight/moment would be hard to compute, we
>figured putting it on the scales would be a good plan.
>
>Old calculated weight: 1307
>New measured weight: 1379

I would not worry that much, my '71 180F weighs in at 1448 empty !

[Brien K. Meehan]

wrote:
> Maybe *I* need to go on a crash diet before the big AK trip... :)

I would call it an anti-crash diet.

[[email protected]]

LOL... yeah, I guess one could call it that. :)

My biggest irritation is that the upholstery place used some thicker material
than I had thought... probably close to 10 lbs more cardboard and foam than necessary.
Oh well, at least it looks good and it's *MUCH* quieter with an interior.

Who'da thought that a -180 would be marginal for a cross-country with only two
people? 200 lbs of gear for two guys isn't that much for a big cross country like
that.

-Cory

: wrote:
: > Maybe *I* need to go on a crash diet before the big AK trip... :)

: I would call it an anti-crash diet.


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Matt Barrow]

> wrote in message
...
> We finally did it.... we had to weigh the airplane. After three years of
> owning it, upgrading radios, adding whatzits (Tannis heater, vacuum
filter, new
> strobe, etc), we finally had a custom interior made up for it. Since the
last
> weighing was without an interior and the weight/moment would be hard to
compute, we
> figured putting it on the scales would be a good plan.
>
Why in hell did you go for a Tanis heater instead of Reiff?

[Margy]

Jay Honeck wrote:
>>I did some recent calculations for an upcoming trip via helicopter we are
>>taking in Australia with friends. Total allowed weight = 700 lbs
>>Total combined weight for the 4 of us = 638 lbs Total weight lost by all
>>of us since Christmas break = 90 lbs. I'm really glad the diets worked!!
>
>
> I *thought* you guys looked thin(ner), but never had the chance to say
> anything. Good job!
>
> 90 pounds -- wow!
Ron and I only account for 50 of that!

[Bob Noel]

In article >,
Aaron Coolidge > wrote:

> wrote:
> : Old calculated weight: 1307
> : New measured weight: 1379
>
> Mine - 1968 180-D - weighs 1400 lbs, the lightest it has ever weighed.

oh heck, my '74 140 weighs 1437 lbs.

--
Bob Noel
no one likes an educated mule

[[email protected]]

Matt Barrow > wrote:
: Why in hell did you go for a Tanis heater instead of Reiff?

- Get heat *AT* the head... not at the other end of the jug where it has to go
by cooling fins designed to remove it to get where it's needed.
- We already had spark-plug CHT probes.
- We found an ebay deal.

My thinking is unless you had a good reason not to, Tannis is the better way
to go. Why do you think differently?

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[[email protected]]

Aaron Coolidge > wrote:
: Mine - 1968 180-D - weighs 1400 lbs, the lightest it has ever weighed.
: --

Guess that makes me feel better. I just get a little gunshy when flying it
close to gross since the climb performance *really* goes to crap in the PA-28 when
approaching gross.

The other thing is a resale issue. Since ours was a -140 that's been upgraded
to -180, its legal max gross weight wasn't (appreciably) increased. It's legal only
to 2200 gross TO (2150 landing)... if it were a real -180 it'd be legal to 2400.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Dave Butler]

wrote:
> Matt Barrow > wrote:
> : Why in hell did you go for a Tanis heater instead of Reiff?
>
> - Get heat *AT* the head... not at the other end of the jug where it has to go
> by cooling fins designed to remove it to get where it's needed.

That's interesting. I've never owned a heater, don't know about Tanis or Reiff,
since I've been flying, I haven't lived in a climate where heating is called
for, but...

I'd think "at the head" is not a particularly important place to have the heat.
Seems to me heating the oil in the crankcase so it can be pumped more quickly
and start lubricating is a better bang for the buck.

.... or maybe the rationale is that heating the head relieves the "choke" of the
cylinder barrel and reduces wear that way? If so, I have to wonder whether the
few degrees rise you're likely to get from an electric heater has any
significant effect on the amount of choke.

Why heat the heads?

Ignorant and looking to learn... Dave

[Mike in GR]

"Dave Butler" > wrote in message
news:1119360233.195544@sj-nntpcache-3...
> That's interesting. I've never owned a heater, don't know about Tanis or
> Reiff, since I've been flying, I haven't lived in a climate where
> heating is called for, but...
>
> I'd think "at the head" is not a particularly important place to have
> the heat. Seems to me heating the oil in the crankcase so it can be
> pumped more quickly and start lubricating is a better bang for the buck.
>
> ... or maybe the rationale is that heating the head relieves the "choke"
> of the cylinder barrel and reduces wear that way? If so, I have to
> wonder whether the few degrees rise you're likely to get from an
> electric heater has any significant effect on the amount of choke.
>
> Why heat the heads?
>
> Ignorant and looking to learn... Dave

2 reasons to preheat- Lycoming et-al want you to preheat for damage
issues, i.e. choke and oiling as you mentioned. The second reason for heat
though, is to get the pig to start in the first place.

Also, a full Tanis set-up has a small heater for each cylinder and a pad
on the pan to warm the oil.

Mike Z

[Matt Barrow]

> wrote in message
...
> Matt Barrow > wrote:
> : Why in hell did you go for a Tanis heater instead of Reiff?
>
> - Get heat *AT* the head... not at the other end of the jug where it has
to go
> by cooling fins designed to remove it to get where it's needed.
> - We already had spark-plug CHT probes.
> - We found an ebay deal.
>
> My thinking is unless you had a good reason not to, Tannis is the better
way
> to go. Why do you think differently?

Based on what Aviation Consumer had to say when I was buying a system
(March, 2001 edition). They said there was no advantage to merely heating
the head and that heating the barrel did have advantages.

Aviation Consumer, March 2001, pg. 18

"[Other brand] loses us in claiming that the top of the cylinder is more
critical to heat than the rest of the cylinder."
"As for heating the top of the cylinder being better, we just don't buy
that."
"As for bands versus cylinder head plugs, our view is that [other brand]
overstates the case in saying it's best to heat the head."


Cost - about a factor of three for the Tannis, would have added a couple
thousand $$ to the total cost including installation and paperwork.

Total cost for my Reiff system, including installation was under $1000.

AIUI, Tannis does heat the cylinder with the factory CHT probe. It also
causes problem for the CHT probes that you add for an engine analyzer.

http://www.reiffpreheat.com/FAQ.htm#QA10

FWIW, this if Reiff's take, but then Tannis has there's which is not
supported by third party reviews.

Aviation Consumer, TCM and the shop that did my engine conversion all
advised going with the Reiff.

YMMV.


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

[Matt Barrow]

"Mike in GR" > wrote in message
ink.net...
>
>
> "Dave Butler" > wrote in message
> news:1119360233.195544@sj-nntpcache-3...
> > That's interesting. I've never owned a heater, don't know about Tanis or
> > Reiff, since I've been flying, I haven't lived in a climate where
> > heating is called for, but...
> >
> > I'd think "at the head" is not a particularly important place to have
> > the heat. Seems to me heating the oil in the crankcase so it can be
> > pumped more quickly and start lubricating is a better bang for the buck.
> >
> > ... or maybe the rationale is that heating the head relieves the "choke"
> > of the cylinder barrel and reduces wear that way? If so, I have to
> > wonder whether the few degrees rise you're likely to get from an
> > electric heater has any significant effect on the amount of choke.
> >
> > Why heat the heads?
> >
> > Ignorant and looking to learn... Dave

(See the URL summary in previous post)

>
> 2 reasons to preheat- Lycoming et-al want you to preheat for damage
> issues, i.e. choke and oiling as you mentioned. The second reason for heat
> though, is to get the pig to start in the first place.
>
> Also, a full Tanis set-up has a small heater for each cylinder and a pad
> on the pan to warm the oil.
>
Tannis (AIUI) does not head the head which has the CHT probe, or did they
develop a plug that can co-locate the CHT probe AND the heater element? I
don't think they had one in 2001.

[Matt Barrow]

> wrote in message
...
> Matt Barrow > wrote:
> : Why in hell did you go for a Tanis heater instead of Reiff?
>
> - Get heat *AT* the head... not at the other end of the jug where it has
to go
> by cooling fins designed to remove it to get where it's needed.

That's not only a myth, but flat out wrong.

http://www.reiffpreheat.com/FAQ.htm#QA11

[[email protected]]

: > Matt Barrow > wrote:
: > : Why in hell did you go for a Tanis heater instead of Reiff?
: >
: > - Get heat *AT* the head... not at the other end of the jug where it has
: to go
: > by cooling fins designed to remove it to get where it's needed.

: That's not only a myth, but flat out wrong.

: http://www.reiffpreheat.com/FAQ.htm#QA11

I can see I stirred up a hornet's nest here. I don't care all that much
either way... I looked into it awhile back and decided that with appropriate
workarounds, Tannis provides better performance where it matters. In response to your
previous messages:

- Tannis does have workarounds for the CHT probe. I think they've got a combo
thermocouple and heater element, but I just use the spark-plug probes. They've also
got the extra-kludgy valve cover gasket heater... ick!

- Cost... yeah, that makes a difference. I got mine used.

- My statement regarding heat AT the head was poorly worded, but my point still
stands. I was not talking about interfering with cylinder cooling
(http://www.reiffpreheat.com/FAQ.htm#QA11)... rather the argument that heat flows well
the other way. If you read their rebuttal (http://www.reiffpreheat.com/FAQ.htm#QA10)
carefully, you see:

"Our testing of our system and the other brand showed that the cylinder temperature
measured at the top end of the cylinder mid-way between their element and ours was the
same with both systems. Not surprising since both are 50 watt heaters. They did a
test too, but they skewed the results in their favor by measuring the temp about 1
inch away from their heating element."

No surprise there... if you look at the cylinder, a point midway between the
CHT probe and the base of the cylinder barrel has almost the same amount of barrel
travel. Heat *will* flow in all directions from the source, but if you heat in the
center of the head, it'll get more heat *IN* the head than if you heat from the bottom
of the jug. The head is where the choke is, where the highest thermal load is once it
starts (read: uneven expansion initially).

Don't get me wrong... both products have issues, and they both are flinging
crap at the other to try to say that theirs is better. Aside from the expense and
complication of heating *all* cylinders (including ones with CHT probes), the Tannis
is a better engineered solution.... put heat where it's necessary. If you could seal
off and insulate the cowling extremely well so little heat is lost, everything inside
would eventually get toasty. In a finite time with imperfect insulation, I'd rather
put the heat where it's necessary.

Flame on... :)
-Cory



--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[[email protected]]

Dave Butler > wrote:
: That's interesting. I've never owned a heater, don't know about Tanis or Reiff,
: since I've been flying, I haven't lived in a climate where heating is called
: for, but...

Generally, the freezing point is about where it's considered a good idea to
preheat. Some people say 40, some 20.

: I'd think "at the head" is not a particularly important place to have the heat.
: Seems to me heating the oil in the crankcase so it can be pumped more quickly
: and start lubricating is a better bang for the buck.

That's important, although with multiweight oils it's less so.

: ... or maybe the rationale is that heating the head relieves the "choke" of the
: cylinder barrel and reduces wear that way? If so, I have to wonder whether the
: few degrees rise you're likely to get from an electric heater has any
: significant effect on the amount of choke.

: Why heat the heads?

: Ignorant and looking to learn... Dave

You got it... there was an article (Mike Busch on avweb?) on the clearance of
the dissimilar metals (pistons and cylinders). There's a point (temperature) where
there is *negative* clearance (i.e. scuffing). If one can warm the thing from 0F to
+40F, you've already gotten past it. Also, the heat loading is uneven due to the
mass. It takes a (relatively) long time for the cylinders and heads to heat up
compared to the lightweight pistons in very close proximity to the fire.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[[email protected]]

Aaron Coolidge > wrote:
: Hi Cory, I think that if you have airflow the head is an efficient heat
: dissipator. If you have no airflow, the metal components of the cylinder
: will eventually get to thermal equilibrium regardless of the position of
: the heating elements.
Correct, but remember this. There *are* heat leaks somewhere or else it would
get hotter and hotter. That means that there's heat flow. AUIU, once the convective
air is blocked, the prop/cranks is the biggest heat sink of all... sucks heat right
out of the case. There *will* be a thermal gradient under the hood... hottest places
at the elements, and coldest at the heat sinks.

I have a reiff system; my plane is kept outside in
: Southeastern MA; I do not have a cowling cover (but the fiberglass
: cowling is a good insulator and I use cowl plugs). I find a 30 deg F rise
: at the cyl head on the coldest days that we experience. I measured 30degF
: at the #1 cyl head with my trusty Omega handheld thermocouple with 0 degF
: ambient. I am satisfied.
Agreed... I generally run the same setup... no cover, but cowl plugs. I
haven't put a thermocouple on them, but at 20F the heads are quite warm to the
touch... I'd say 40-50. Sounds like the same 30 degree rise. With better insulation,
things would be even better.

: I got the Reiff because I can't stand tanis' web site! I was impressed with
: Reiff's after-sale service, as well. When I messed up gluing the heater
: to the oil sump they sent me a new batch of glue. The glue is just metal-
: filled epoxy (think J-B Weld), but I wanted to use their "special" stuff
: anyway.
: --
: Aaron C.

I got mine used, so it was cheaper and didn't have support no matter what.
I'm not saying Reiff sucks. It's much better than leaving one cylinder without heat
IMO. I'm just saying that aside from that issue with the Tannis, Reiff bands will
probably perform "up to and possibly including" tannis performance... :)

-Cory
--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Matt Barrow]

"Mike in GR" > wrote in message
ink.net...
>
>
> "Dave Butler" > wrote in message
> news:1119360233.195544@sj-nntpcache-3...
> > That's interesting. I've never owned a heater, don't know about Tanis or
> > Reiff, since I've been flying, I haven't lived in a climate where
> > heating is called for, but...
> >
> > I'd think "at the head" is not a particularly important place to have
> > the heat. Seems to me heating the oil in the crankcase so it can be
> > pumped more quickly and start lubricating is a better bang for the buck.
> >
> > ... or maybe the rationale is that heating the head relieves the "choke"
> > of the cylinder barrel and reduces wear that way? If so, I have to
> > wonder whether the few degrees rise you're likely to get from an
> > electric heater has any significant effect on the amount of choke.
> >
> > Why heat the heads?
> >
> > Ignorant and looking to learn... Dave
>
> 2 reasons to preheat- Lycoming et-al want you to preheat for damage
> issues, i.e. choke and oiling as you mentioned. The second reason for heat
> though, is to get the pig to start in the first place.
>
> Also, a full Tanis set-up has a small heater for each cylinder and a pad
> on the pan to warm the oil.
>

As does Reiff, and it has a thermostat that Tanis doesn't.

[[email protected]]

Matt Barrow > wrote:
: As does Reiff, and it has a thermostat that Tanis doesn't.

How many watts for a comparable system? I'm just thinking of the failure mode
of the thermostat. It certainly *would* be nice to plug it in and know it's not
cooking if it gets too warm out.



--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Matt Barrow]

> wrote in message
...
> Matt Barrow > wrote:
> : As does Reiff, and it has a thermostat that Tanis doesn't.
>
> How many watts for a comparable system?

??? watts how?

> I'm just thinking of the failure mode
> of the thermostat. It certainly *would* be nice to plug it in and know
it's not
> cooking if it gets too warm out.

http://www.reiffpreheat.com/Thermostat.htm

http://www.reiffpreheat.com/DigitalTimer.htm

[Newps]

The most important thing to heat is the oil, if you can only heat one
thing. I have two heat pads on my oil sump on my 182 and that's it.
Tanis and Reiff work but are only of value if you can't cover the engine
compartment. I have a Kennon cover for mine and the whole engine
compartment is a toasty 80F while the oil is 100F.

wrote:

> Dave Butler > wrote:
> : That's interesting. I've never owned a heater, don't know about Tanis or Reiff,
> : since I've been flying, I haven't lived in a climate where heating is called
> : for, but...
>
> Generally, the freezing point is about where it's considered a good idea to
> preheat. Some people say 40, some 20.
>
> : I'd think "at the head" is not a particularly important place to have the heat.
> : Seems to me heating the oil in the crankcase so it can be pumped more quickly
> : and start lubricating is a better bang for the buck.
>
> That's important, although with multiweight oils it's less so.
>
> : ... or maybe the rationale is that heating the head relieves the "choke" of the
> : cylinder barrel and reduces wear that way? If so, I have to wonder whether the
> : few degrees rise you're likely to get from an electric heater has any
> : significant effect on the amount of choke.
>
> : Why heat the heads?
>
> : Ignorant and looking to learn... Dave
>
> You got it... there was an article (Mike Busch on avweb?) on the clearance of
> the dissimilar metals (pistons and cylinders). There's a point (temperature) where
> there is *negative* clearance (i.e. scuffing). If one can warm the thing from 0F to
> +40F, you've already gotten past it. Also, the heat loading is uneven due to the
> mass. It takes a (relatively) long time for the cylinders and heads to heat up
> compared to the lightweight pistons in very close proximity to the fire.
>
> -Cory
>

[Matt Barrow]

"Newps" > wrote in message
...
> The most important thing to heat is the oil, if you can only heat one
> thing. I have two heat pads on my oil sump on my 182 and that's it.
> Tanis and Reiff work but are only of value if you can't cover the engine
> compartment.

Both Tanis and Reiff recommend an engine cover and plugs. Reiff (maybe
Tanis, too) recommends a prop cover as well.

> I have a Kennon cover for mine and the whole engine
> compartment is a toasty 80F while the oil is 100F.

I don't normally use a cover (cowl plugs), but it's in an unheated, hanger
with electricity. A thermostat kicks in when the air temp drops below 40F.

After 12 hours the oil and CHT's are over 100F and when I kick on cabin
heat, it's toasty in a few minutes.

Something else no one mentioned yet is a battery heater.

We don't get the extreme cold your northerners do here in Western Colorado,
but sub zero is not uncommon during winter.

In any case, with a Turbo'ed engine, cold starts are killers (not to sya
they aren't traumatic for NA plants as well).


--
Matt
---------------------
Matthew W. Barrow
Site-Fill Homes, LLC.
Montrose, CO

[Jay Honeck]

>> I *thought* you guys looked thin(ner), but never had the chance to say
>> anything. Good job!
>>
>> 90 pounds -- wow!
> Ron and I only account for 50 of that!

"Only" 50???

Fifty pounds is awesome. I've lost 20, and feel great, by eating fruit.
How'd you guys manage it?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Flyingmonk]

I have been gaining gradually 1-2 pounds a month. I gotta do something
quick! I don't want you guys to have to read about them cutting up my
house to get me out!

Bryan "The Monk" Chaisone

[Doug]

Never weigh an airplane. Use the weight in the book. You will be able
to carry more doing it this way. It's even legal.

[Newps]

Doug wrote:
> Never weigh an airplane. Use the weight in the book. You will be able
> to carry more doing it this way. It's even legal.

Go ahead and weigh it. If you don't like what you see then forget all
about it. That's legal too.

[[email protected]]

Newps > wrote:
: Go ahead and weigh it. If you don't like what you see then forget all
: about it. That's legal too.

That was sorta the plan. Trouble is, we did so many things to the plane, that the W&B changes were hard to compute.
Especially for the interior... very nebulous as far as the moment of all the little pieces.

Just for the record, we got our gear loaded to within our target weight and made it to AK. Now, just to get back in
10 days... :) It sure didn't want to climb much over 5000' with it as hot as it was over IN. Probably 200-300 fpm at 7000'
DA, 50 lbs under gross.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Jay Honeck]

> Never weigh an airplane. Use the weight in the book. You will be able
> to carry more doing it this way. It's even legal.

Agreed.

Does anyone know how they compute the maximum allowable take-off weight
(and, thus, the useful load) of a Spam Can like we fly? I assume it's got
something to do with minimum climb performance, but what are the parameters?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Jay Honeck]

>> Does anyone know how they compute the maximum allowable take-off weight
>> (and, thus, the useful load) of a Spam Can like we fly? I assume it's
>> got something to do with minimum climb performance, but what are the
>> parameters?
>
> I don't think there's a general answer. I think the answer has to be
> specific to the model you're asking about. For one, it might be climb
> performance, for another the wing spar strength, for another landing gear
> strength, for another control authority, etc.
>
> It's one of those bottleneck performance questions where you beef up one
> area only to find out that just gets you to the next bottleneck.
>
> I don't think there's anything in the public record that specifies what
> the limiting parameter is for given type certificate.

Well, taking our Pathfinder as an example, somehow Piper managed to get a
1400+ pound useful load out of a 235, which is a huge difference from the
180.

True, that's a 30% horsepower increase, and Piper did have to beef up the
sheet metal in some places, but essentially they got the greatest useful
load of any GA 4-seat plane by simply slapping a 6-cylinder engine on the
front of an Archer.

But how did they determine what that useful load was? Did they keep adding
lead ingots until the plane couldn't climb more than "x" feet per minute?
Did they keep landing it at greater weights until the gear failed? You
always hear stories about the guy who "flew out with a moose in the back" --
which implies that useful load is set conservatively, with at least some
margin or fudge-factor built in.

I kick myself for not asking this at the Cherokee Pilots Association fly-in
last year. One of the original Cherokee designers was the keynote speaker,
and I'm sure he could have answered this question. (Chuck Suma, president
of New Piper, is the keynote speaker this year -- so maybe I'll ask him...)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[George Patterson]

Jay Honeck wrote:
>
> But how did they determine what that useful load was? Did they keep adding
> lead ingots until the plane couldn't climb more than "x" feet per minute?

They start by calculating the performance. Then they do take it up with weight.
Maule uses 50lb sacks of lead shot. Frequently the limiting factors are stall
speed and the requirement that the plane be able to climb with full flaps on a
standard day. Maule had to reduce the flap setting on the MX-7-160 after tests
showed it wouldn't do that at max gross.

> Did they keep landing it at greater weights until the gear failed? You
> always hear stories about the guy who "flew out with a moose in the back" --
> which implies that useful load is set conservatively, with at least some
> margin or fudge-factor built in.

Any light plane will fly when overloaded. Usually they can get off the ground at
about 1.5 times max gross, and this is sometimes done for overseas ferry
flights. You know from your experience in that Cessna 150 how this affects the
performance -- long takeoff runs and poor climb rates. Sometimes the W&B
envelope gets narrower at high loadings also. IMO, this is not a margin or
fudge-factor.

George Patterson
Why do men's hearts beat faster, knees get weak, throats become dry,
and they think irrationally when a woman wears leather clothing?
Because she smells like a new truck.

[Jay Honeck]

> Any light plane will fly when overloaded. Usually they can get off the
> ground at about 1.5 times max gross, and this is sometimes done for
> overseas ferry flights. You know from your experience in that Cessna 150
> how this affects the performance -- long takeoff runs and poor climb
> rates. Sometimes the W&B envelope gets narrower at high loadings also.
> IMO, this is not a margin or fudge-factor.

Thanks, George.

I guess it all comes down to what you're comfortable with, and what your
plane will do. I've flown my 235 at gross many times, without difficulty,
which always makes me wonder what the REAL capability of the plane is...

With our plane, though, we run out of internal room long before we run out
of weight-carrying capacity. It's a nice change, after all those years of
sweating weight and balance.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"