The contentious issue of the use of the Carburettor Heat

[crazy_aviator]

Observing 2 engine induction fires in 1 week in 2 different A/C by a person pumping the throttle tells me that it CAN be done improperly !!!

[Big Pistons Forever]

Observing 2 engine induction fires in 1 week in 2 different A/C by a person pumping the throttle tells me that it CAN be done improperly !!!

The only induction fire I have ever seen on a small carburated engines was caused by gross over priming on a very cold day. As Hedly pointed out the only caution is to make sure you pump the throttle only after the starter has started rotating the prop.

[MichaelP]

WhoooOOOP! WhoooOOOP!

Making an aircraft engine sound like this by pumping the throttle is verboten when I'm in the aeroplane and in any aeroplane I'm likely to fly...
Do this to a geared engine and be prepared to pay a BIG bill!

I have started a lot of engines, I was/am known to be able to start almost anything, but I never have needed to pump the throttle while cranking.
I would never abuse an aircraft engine because I have to do such a technique on a racing car engine!

I say that if this technique is the only way to start your engine you need to take it to another mechanic and have it looked at!

However, with an O-200 and no primer pump, on a cold day I used to pump suck pump suck pump suck suck, and then she was ready to start. I still did not pump while cranking.
It was so easy to get a backfire with a wooden propeller (they're lighter than metal ones with less momentum to keep it turning the proper way).

[Hedley]

induction fires ... pumping the throttle tells me that it CAN be done improperly

Of course! I never said it couldn't ... in fact, if you go back
and re-read what I said, I started off with a warning that this
technique was NOT for the youngsters here, who wouldn't have
a clue what the difference between the idle speed and idle
mixture screws on the carbureter.

Do this to a geared engine and be prepared to pay a BIG bill!

Michael, please re-read the above paragraph. With all due
respect, I suspect that I fly more geared engines than you -
for example, the C421 has GTSIO-520 TCM engines, and the
clip-wing 700hp supercharged R-1340 Harvard I fly aerobatics
in has been modified with an enormous geared 3-blade prop
that almost touches the ground in the 3-pt attitude. Etc.

I never have needed to pump the throttle while cranking

That's a sophomoric argument, Michael. Just because you
have never used (or needed) that technique doesn't mean
it doesn't work, or it isn't necessary sometimes.

I don't think you can claim that you have flown all aircraft ever
made under all conditions that have ever existed

For example, have you tried to start a PT-22 Ryan with
an R-56 Kinner radial engine in Ontario in February?

I have, and let me tell you, that since it doesn't have
a primer, you'd better get used to pumping the throttle
until the fuel runs out the bottom cowling if it's going to
start. Not all of us have spent our entire flying careers in
mild England or gentle BC.

Again, I didn't say that this technique was without
risk. But sometimes, it's all you've got. For adults
only, ok? Caveat Emptor, and if you don't like what
I have learned after over 30 years of operating many
different kinds of piston aircraft (and auto and boat
and motorcycle) engines, you really don't to read it,
or like it, or even pay attention to it.

Feel free to make your own mistakes, and not learn
from the experience of others.

[MichaelP]

For example, have you tried to start a PT-22 Ryan with an R-56 Kinner radial engine in Ontario in February?

I've never seen a Kinner radial on anything that most people are likely to be flying on this forum.

I've primed by both use of the primer and by priming on the throttle.
In the winter I prime and suck it in by hand by either method and I get the engine to start with reasonable ease.
I have operated engines in extremely cold temperatures, and very hot ones too.
IMHO pumping the throttle to get a start is probably best left to private personal time

I too have 35 years flying experience in something over 120 different types of piston engined aeroplanes. I'm just saying the following:

1. I have never needed to pump the throttle.
2. I would not want to see this technique used in any aeroplane I'm associated with.

That's my opinion

[Hedley]

I too have 35 years flying experience

I guess the difference between the two of us, Michael,
is that I'm always willing to learn something new, that
I don't know yet.

Unlike you, I cannot claim to have flown every aircraft ever
built under every condition that has ever existed, and thusly
I cannot claim that I am in possession of all aviation knowledge,
which I understand is your argument here.

[MichaelP]

For example, have you tried to start a PT-22 Ryan with an R-56 Kinner radial engine in Ontario in February?

I admire you for flying open cockpit in February...
I did it once in a Tiger Moth, my cheeks froze as I flew over East London to Panshangar... Someone had a flask of coffee in the hangar and that was very very welcome before I had to fly back again.

I spent seven winters in Montreal, I know what it's like to be so cold that it would be so easy to lie down on a soft white glistening snow bank and go to sleep.

Nope, open cockpit in February anywhere but close to or south of the Equator is not for me.

I guess the difference between the two of us, Michael, is that I'm always willing to learn something new

Something new????
This is not something new... I've seen pilots do this in the past a few times, often without success.
I've even rectified their flooded engines and started them without pumping the throttle.

You have to understand that I've seen a lot of really stupid things done to and in aeroplanes and some things I take exception to.
You are welcome to your point of view on this one.
But as I say, what people do in their own aeroplanes is their business until it has an impact on my aeroplanes and perhaps the safety of all around.

I have the right to ban such procedures in aeroplanes under my care, and I will do so.
If I catch anyone pumping the throttle in one of my aeroplanes I'll give them remedial training. If they do it again (unlikely!) then we'll go to the next level!

This weekend I was reminded of an incident a few years ago.
A couple of chaps asked me to look at the Myth, a homebuilt wood and fabric Moth-alike that they were considering buying. It had sat outside at Delta Airpark for many years. Delta Airpark is on the coast and subject to damp and salt.
The rear fuselage was completely unglued and rotted...
A weekend or two later I was shocked to see this aeroplane flying with a pilot giving joy rides...
What am I to do?
Do what most people do and turn a blind eye?
No.
How can any responsible person say nothing while innocent people are put in peril.
I walked up to the aircraft and told the pilot quietly about what the condition of his aircraft was. He responded by threatening me with violence.
What can I do???
A couple of years ago he told me he kept the aeroplane to 60 knots... Was that enough?

There are some people who live charmed lives, get away with doing stupid things in aeroplanes, and live a long time.

When I read of doing an inverted loop from ground level I believe the pilot lives a charmed life. I have known pilots do such things in the past and who are no longer with us.

We should be careful about what we suggest to people.

Pumping the throttle is not in any approved procedure for Lycoming and Continental engines. It is an unnecessary procedure in these.
Prepared properly these engines start with much safer procedures.

And back to the carb heat... It should be used and used according to the recommendations of the engine and airframe manufacturers.
It should not be used as an excuse for an accident when the real reason lies elsewhere. We owe it to our fellow aviators to give correct information as to the cause of an accident so that we all can learn.

[Hedley]

I admire you for flying open cockpit in February

My grandfather and his brother did it regularly in World War One,
so I figure once in a while probably won't kill me, although I am
certain I am nowhere near as tough as they were.

an inverted loop from ground level ... pilots do such things in the past and who are no longer with us.

A little off-topic, but I'll let you in on a secret:

Anything is easy, if you know how.

Many pilots have died, merely when trying to fly straight
and level in good weather. Based on that data, would
you conclude that no one should try to fly straight and
level in good weather?

If you want a real challenge, try a surface outside loop
as wing in line abreast formation. It's over 10x as difficult
as the solo version, IMHO. No one does them except us,
and there's a reason for that.

I'm not sure anyone here cares about the facts - everyone
here seems to be some kind of uber-expert on everthing,
including surface-level aerobatics, despite the fact that they
know nothing about it - but what keeps you alive, doing
downward-looping vertical aerobatics at low altitude (either
positive or negative G, doesn't matter) is the application of
something called a "top gate" and to a lesser extent an "entry
gate" (more applicable to co-ordinating formation aerobatics,
actually). You would probably be greatly surprised as to
which of the top gate parameters is more important. Most
people are.

Of course, the technique for the pull during the downward-looping
maneuver is important as well, for minimum altitude loss.

I am only a graduate engineer (defrocked mathematician,
actually) and physics geek, but I wrote a note on that
particular subject a few years back, which you might
find surprising:

http://www.pittspecials.com/etc/airspeed_radius.htm

When I am in a vertical downline in a low-altitude aerobatic
maneuver, the first thing I do for minimum altitude loss is
apply full power.

This is obvious, when you think about the physics, which
few people comprehend.

Anyways, aerobatics is merely applied physics. If you don't
understand physics I can see how you might think someone
who does is "charmed".

A couple weeks ago, I was flying a surface level inside
loop (yawn) and over the top, I noticed that my altimeter
was reading less than 1,000 (I zero it on the ground). So
I didn't pull through, I just let the nose drop to the inverted
45 and did a 1/2 cuban to exit.

In a Pitts, at my density altitude, my "top gate" for a loop
or reverse cuban-8 is 1,000 AGL. If I don't have that,
I don't pull (or push) through.

It's that simple.

Anything is easy, if you know how.

I will leave it as an exercise for the reader to determine
the effect of density altitude and aircraft stall speed on
the top gate, which ought to be frikken obvious if you
think about it for more than 10 seconds.

[MichaelP]

No one does them except us, and there's a reason for that.

Agreed 100%....

I teach aerobatics and such things are not for me!

aerobatics is merely applied physics

Disagree... If that was the case we'd know the atmosphere well enough to predict the weather with 100% accuracy.
In still air at a known temperature with precise lapse rate I am sure you can work out the exact G, airspeed over the top and all other factors and fly the aeroplane with precision around an outside loop from ground level.

But the air is a fickle thing and one day these calculations and their allowances are exceeded and we'll read another obituary.
Believe me I have known some of the best reputed pilots in this world who are now no longer with us after they have piled Spitfires, Heinkels, and Lightenings into the ground.

Here in BC we have a resurgence of the Aerobatic Club aerobaticsbc.wordpress.com and we'll produce some more aerobatic pilots to compete and perhaps perform in the future.
To be an aerobatic pilot for competitions you need to practice 15 minutes every night to be good enough... Competition is like the Olympics and it takes practice to become perfect.
This was the case with the Tiger Club where competition pilots would do their 15 minutes over the airfield every evening in the Stampe.
The Boss when I joined was Neil Williams who flew a Jungmann superbly doing a double flick roll on short finals and landing. "Get Home Itis" got him in the end. IMC in the mountains.

There are ways of doing things and these take practice.
There is also decision making and this above all else keeps one safe.

[Hedley]

I have known some of the best reputed pilots in this world who are now no longer with us after they have piled Spitfires, Heinkels, and Lightenings into the ground.

Sigh. Do you know what a Venn diagram is, Michael?

http://en.wikipedia.org/wiki/Venn_diagram

In one circle is the set of pilots who are really good - even
phenomenal - stick and rudder pilots. Much better than I
am, many of them.

In another circle is the set of people who understand the
underlying applied physics which is aerobatics. Many of
them are much smarter than I am.

However, there is a very very slim overlap of the two
circles, which is where you will find pilots that can safely
perform low-altitude aerobatics.

Your contempt towards the physics shows that you
do not understand it. Your choice to not perform low
altitude aerobatics, in light of that, is a good one.

For many years, I have been told by many people,
whom are neither particularly good sticks, and don't
understand any mathematics, that I am "dangerous".

Over those years, many pilots have died, but I am
still alive. I am sure it is merely a coincidence.

Another angle, Michael: every time a large aircraft
flies an approach, the crew calculates a Vref based
on the physics of the situation. Is that dangerous?
Should no one ever attempt to fly an approach in
a large aircraft because of the calculation required?

Similarly, before a large aircraft performs a takeoff,
calculations will be performed for the balanced field
length, Vr, V1, etc. In your opinion, is this more
nonsensical physics mumbo-jumbo? Is every crew
of a large aircraft heading for disaster because of
the analytical approach taken?

[iflyforpie]

So Hedley, would this be an example of failing to reach (or improperly calculating) top gate?

http://www.youtube.com/watch?v=dohKKp0EvTs

On topic, (or back to the original hijack) I don't see what the problem with pumping the throttle is provided:
-All other avenues of starting the engine have been exhausted.
-It doesn't make the RPM of the engine surge.
-It is done while the engine is being cranked and in moderation.

I had a primer go in a Cherokee 140 I was flying to Princeton from Chilliwack. My choices were:
-Repair the primer with automotive O-rings.
-Abandon the aircraft in YDC, take the bus home, and take the bus back with a $3 set of approved O-rings.
-Pump the throttle and fly home.

I chose #3 and it started on the second try with no backfire.

[MichaelP]

I have no objection to giving the throttle a couple of pumps and then starting it.
I do not see the efficacy of pumping while turning with the mags on...

I pump and suck in by hand in the winter and it always works. In the Cherokee a couple of pumps and then turning the prop either by hand or with the starter is not a problem.
But masterbating the throttle is!
How can you estimate the amount of prime the engine needs; whether it's too much or too little?

Over those years, many pilots have died, but I am still alive. I am sure it is merely a coincidence.

You're a charmed person.
I've known many who get away with stupid things and a few who made one mistake and died.

Another angle, Michael: every time a large aircraft flies an approach, the crew calculates a Vref based on the physics of the situation.

Yes, but they are not doing an inverted approach!
They also use high safety factors.

I explain it this way:
At altitude you loop and you note the amount of height used and find your "top gate".
Then you try it from close to the ground... But seeing the ground so close you don't do the loop perfectly, you pull a little more and rather than tightening the loop the additional drag widens it and you smack the ground and die.
Look at the videos of Spitfires crashing this way, high speed stall with the aeroplane continuing downwards.

This is not professional physics flying of airliners this is man and machine and man is fallible.

[Hedley]

So Hedley, would this be an example of failing to reach (or improperly calculating) top gate?

http://www.youtube.com/watch?v=dohKKp0EvTs

Exactly! Famous accident. The problem is that above 3,000
the poor pilot couldn't zero his altimeter, so he had to do some
mental arithmetic - which he did wrong - and his top gate was
too low, and he hit the ground. It didn't matter what airspeed
or G he used, he was going to hit the ground.

I've known many who get away with stupid things

My application of physics to create safe procedures for aerobatics
is stupid? You do realize the irony here, of you - a non-practitioner -
telling a practitioner that he doesn't know what he is doing, and
that is it merely coincidence that all his flights over all the decades
"just happened" to conclude safely

Would I be correct to conclude that you did not study
mathematics or physics at the post-secondary level?

Michael, a cave man who saw a television set would
almost certainly conclude that it was magic, because
he didn't understand the physics behind it.

You're a charmed person

Yes, and a television is magic

[square]

I saw my DOM have to pump the throttle while cranking to get one of those new 172 engines going -- which had been outside without heat in -35 for a couple days. Priming with the injectors just didnt work. It was a pretty ugly start but got er going.

[MichaelP]

My application of physics to create safe procedures for aerobatics is stupid? You do realize the irony here, of you - a non-practitioner - telling a practitioner that he doesn't know what he is doing

The response to that quote is this quote:

Over those years, many pilots have died, but I am still alive. I am sure it is merely a coincidence.

Then:

My application of physics to create safe procedures for aerobatics is stupid?

Yes because you are applying it to the human being who has a multitude of fallibilities starting with if and what he ate for breakfast that day, how much sleep he got etc etc.

I see myself make mistakes, most human beings do, and so we allow for human error by using checklists and memory items and procedure to keep us safer.

That extra half a G you push or pull one day because of the physical condition of the day will bite you when you leave yourself no margin for error.
A loop from ground level to ground level even with the correct top gate has no margin for error...
We get away with things... and then we don't.
Like you I have got away with a few low level manoeuvres in my time, and like many I've had my heart in my mouth and thanked 'non physics' in the way of luck that I got away with it.

I have also had a throttle fail on me when the cable broke.
I teach people to treat all the controls with care, apply enough input and only enough, do everything smoothly.
Masterbating the throttle is not smooth, and is an abuse of a mechanical thing.

[Hedley]

Like you I have got away with a few low level manoeuvres

No, you are completely wrong. I have not "gotten away"
with a few low altitude maneuvers, I have done many thousands
of them, after considerable practice and planning.

thanked 'non physics' in the way of luck that I got away with it.

The more physics I learn, the "luckier" I get.

a cave man who saw a television set would
almost certainly conclude that it was magic, because
he didn't understand the physics behind it.

Just because you can't fix a TV, Michael, doesn't
mean no one else can (or should).

outside without heat in -35

Ether will start an aircraft engine at very low
temperatures without preheat. I don't recommend
it because of the damage that will likely result,
but if you've got the bucks to spend, the reduced
TBO won't bother you.

[MichaelP]

Was Newton lucky when an apple fell on his head?
What is modern physics version of the apple?
I suppose a sub-atomic particle hurts less....

Television used to be magic, now it's so much rubbish I hardly watch it.

Just because you can't fix a TV, Michael, doesn't mean no one else can (or should).

It seems nobody can fix North American TV now...
I've banged a few televisions with my fist when they didn't work, but I wouldn't treat an aeroplane like that. Now I just don't bother with television, I don't have cable.
You could say pumping the throttle is similar to banging the television, both are violent acts of frustration.

I would not advocate calculating how close one can safely come to death, however good one's maths and physics is, and however powerful the computer program you write for it.

[Hedley]

I would not advocate calculating how close one can safely come to death

That's a truly bizarre comment, coming from a pilot.

Every time you step into a certified aircraft, you are betting
your life that the calculations involved in the aircraft structure
design and manufacturing process and life are correct.

If the wing comes off, Michael, you are dead, dead, dead.

According to you, it's time for you to stop flying. And,
you should probably never drive a car, either - ever think
about who designed and manufactured your brakes?

[trampbike]

Ah come on you two! You both have a whole lot of knowledge and experience and it's really great to read you on this forum, since there is a lot to be learned from guys like you. This WAS a very interesting discussion, but it sadly is now just 2 guys arguing using many false arguments and just attacking each other.

I'd love to continue to read about the real stuff: carb heat use, starting an engine, physics of aerobatics. THIS is awesome stuff.

[iflyforpie]

+1

But the rest makes for entertaining reading.

[MichaelP]

I know, but I blame Hedley, he derailed this thread pumping the throttle (there's an English word for that but I better not put it on here!).
So, it's his fault

As far as calculations are concerned, most of us don't calculate how close our heads come to Earth in an outside loop... That's too near death for me!

I lost two very good friends when the difference between machined threads and rolled threads made itself apparent with the wings coming off a Stampe. The calculations were somewhat wrong then, but that aeroplane used to come home with 7G on the meter at times... Things add up over time.

On the subject

You do not go far wrong when you use the engine and airframe manufacturer's recommendations.
With few exceptions I follow the POH/AFM etc...
We can fly at a much lower power setting in the Cessna 152 than that which is shown in the POH (45%), that's an exception.
Leaning the mixture in the cruise below 3,000 feet PA is also in line with the POH and we won't go the distance if we don't.
Using the carburettor heat is also in the POH but I have never seen 'partial heat' being advocated in any manual I've read.

For Rotax 912 engines you are to apply carb heat for any suspicious problem, but if carb heat does not improve things you're supposed to put it in again. These engines rarely ice, and I think Rotax want you to look for any other problem rather than fixate on carb icing.
Which leads me back to the fact that we should look for other causes of our problems:
Fuel, Ignition, and Mixture.... Is the primer in and locked?

P.S. I just looked at the Eurofox in for its first check... No Carb Heat control is fitted!

[crazy_aviator]

On the starting theme , Ive noticed way too many pilots over fuelling ,,then with the fuel pooling on the ground , they continue to BLINDLY try and try again to start until 1 of 2 things happen ,,either they run the battery dead OR they have an engine fire !!! If it dont start ,,seek wise council and STOP !
Another bit of ignorance ,,,when starting a hot continental injected engine ,,,few pilots flush the system out first
A third bit of ignorance , starting an injected lycoming with the mixture in !!!!
Starting engines below 20F is not wise unless they have been preheated etc !
Allowing ANY fuel to pool anywhere is Verboten !!!

[Hedley]

Personally, I find hot-starting a Lycoming fuel-injected
engine can be MUCH trickier than hot-starting a TCM
fuel-injected engine. The TCM has this wonderful return
line (hinted at above), but the Lyc does not.

I am sure that I will be crapped on from a great height
by the self-proclaimed experts here, but I flood Lyc
fuel-injected engines for every start - hot or cold. With
the mixture full rich and the throttle wide open, flip
the boost pump on. Then mixture ICO, throttle cracked
for cold start, 1 inch for hot start, then crank.

Since the mixture is ICO, no more fuel is going into
the flooded engine. As it cranks over, gas gets cycled
out the exhaust, and at some point there is a combustible
mixture in the cylinders, and it fires. Then mixture in
to keep it running with some more gas, and throttle
as required for desired RPM.

Carbureted engines are really, really easy to start,
either hot or cold, in comparison. You don't even
need to use the primer - you can just pump the
throttle while it's cranking

P.S. TCM fuel injected engines, in my experience,
won't start unless fuel is running out the bottom
of the cowl. This occasionally results in a fire on
the pavement below, but it's no big deal - it gets
blown right out by the prop blast, like a candle.
My biggest worry is someone going bananas
and doing something stupid and running into
the propeller.

Back on the subject of low-altitude aerobatics ...
I know nobody here cares about physics, but
one can objectively apply a simple metric to
any aerobatic maneuver, to measure how "dangerous"
it is to perform at low altitude.

It's really very simple. Think of a car that hits
a patch of ice - it has no traction, so it's going
to continue going in whatever direction it was
going when it encountered the ice. We can
think of that direction as the tangential velocity
vector (TVV).

Very simply put, the greater the angle the
TVV subtends the horizon, the more "dangerous"
a maneuver it is. For example, a roll has a TVV
horizontal, or nearly so - it is very safe. A 1/2
cuban-8 has a TVV of 45 degrees below the horizon.
The most dangerous (loop, rvs 1/2 cu-8, etc)
have a TVV of 90 to the horizon - you are pointed
straight down, and if you haven't arranged
things correctly, the physics of the situation
may dictate that the radius of the pull to the
horizontal may be greater than your height.

Now, I know that this is all too left-brain for
many of you here, who just prefer to worship
the ju-ju of the mountain and the magical TV,
but ...

You can actually apply physics to low-altitude
aerobatics to identify high-risk maneuvers and
develop procedures to safely execute them.

But what would I know, compared to the geniuses
here who know nothing about either physics
or aerobatics?

[crazy_aviator]

Hedley, as far as starting an injected lycoming , Correct , the engine is SAFELY overfuelled for startup in ICO , as far as TCM start-up , the below quote does NOTHING to assist the pilot community in learning the right way to start an engine PERIOD . Ive been more than a quarter century as an AME and have seen COUNTLESS IDIOTS try to start all kinds of engines improperly and ALMOST all of them were pilots , so , you are NOT starting from a very high position in my confidence scale Sir ! BTW, I also fly commercially just in case you think that i dont have a pilots mind and nature also !!!


"P.S. TCM fuel injected engines, in my experience,
won't start unless fuel is running out the bottom
of the cowl. This occasionally results in a fire on
the pavement below, but it's no big deal - it gets
blown right out by the prop blast, like a candle."

[iflyforpie]

I don't know. The fuel can piss out of the manifold and catch fire just as easily on a Lycoming engine as a Continental.

I've got very little experience with hot starting fuel-injected Lycomings (did a portion of my PPL on a 172SP, lots of cold-starts on Mooneys, Maules, and Navajos).

For Continentals, I put the mixture rich, boost pump on, and wait for the sound of the pump to change (as it starts pushing fuel through the injectors), and keep it running after that for a slightly shorter time as a cold start. Pump off, mags, starter, and advance the throttle until the engine catches. It is rare for me to have to try twice and beats the standard three-handed hot start.

If I have to do a standard hot start, I always advance mixture first, then retard the throttle. It is just easier this way and I would rather rev an already warm engine up than have it die because my throttle-mixture maneuver was less than perfect.