PA28 vs C172 carb heat question

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JasonM

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I recently started flying the PA28 and was told on checkout that I did not need carb heat as part of my landing checklist. Is this the norm? I'm just so used to always applying full carb heat when doing my pre-landing checklist.

Is the PA28 less prone to carb ice?
 
yep, this was the one thing i had to get used to. i always used to put the carb heat on under 2000 rpm and while descending in a 172. another thing that is really different is the use of fuel pumps. but since youve been flying a float type carburater 172 is probably wont apply to you.
JasonM said:
I recently started flying the PA28 and was told on checkout that I did not need carb heat as part of my landing checklist. Is this the norm? I'm just so used to always applying full carb heat when doing my pre-landing checklist.

Is the PA28 less prone to carb ice?
Click to expand...
 
Yes, the POH says no carb heat for landing and I don't, but there will be others that will post, soon I'm sure, that you should still do it. The reason, per what I read, is the risk of detonation, which according to others, is a low risk. I did get caught on this going the other way last weekend. I rented a 172 in Chattanooga (I was there for business) and the CFI (since I didn't have time for a Checkout) pointed it out after my GUMPS that I had forgotten it.:eek:
 
It's not being more prone to carb ice, it's a different physical setup firewall forward. In the pa28 the carb is physically located in a different location so that is carb is heated by the engine, thus reducing but not completely eliminating the chance of carb ice.

When in doubt, use carb heat if you are more comfortable but remember to turn it off when you need full,power in a go-around.

In 12 years of owning the cherokee, I think I've used carb heat twice.
 
Here is a question for the collective...other than Cessnas, are there any other airplanes that call for carb heat in the pre-landing checklist? I can't think of any that I have flown. All of the carborated Pipers and Beechcraft as well as the SNJ, B-25 and DC-3 do not call for carb heat before landing unless you experience a problem.
 
I fly a piper Cherokee archer and have been taught to use 3 seconds of carb heat on every downwind gumps check. Part of my 'S' for switches and seatbelts...
 
JasonM said:
Is the PA28 less prone to carb ice?
Click to expand...
Compared to the pre-68 Continental-powered 172's, yes, it is, but that is a function of the engine design rather than the airframe. The carburetor on the Lycoming engines used on the PA28's and post-67 172's (up to the 172Q, which was the last carbureted 172) is bolted to the bottom of the nice, warm oil sump, which keeps the carb body warmer, making it less susceptible to carb icing. The Continental O-300's carburetor is thermodynamically isolated from the engine sump/case, so it gets cold and is more susceptible to carb ice.

For that reason, most planes with one of those Lycoming engines say "Carb heat - as required" rather than "Carb heat - full on" as it says in the 172 manuals. My experience with Lycoming-powered carbureted 172's is that they are just as resistant to carb ice as the same engines in Piper, Beech, and Grumman airframes, but for reasons understandable only to Cessna (maybe their lawyers :dunno:), the later 172 manuals still call for full carb heat in the landing checklist regardless of conditions.

So, in the PA28, if you are experiencing carb ice symptoms at low power, pull it full on and leave it there during the approach to landing. Otherwise, leave it off and let the air filter do its job of helping protect your engine.
 
Hobobiker said:
I fly a piper Cherokee archer and have been taught to use 3 seconds of carb heat on every downwind gumps check. Part of my 'S' for switches and seatbelts...
Click to expand...

Based on what rationale? (If the answer is, "Because my instructor taught me to do it that way," then my next question is, "Why did your instructor say that was important?")
 
Jim_R said:
Based on what rationale? (If the answer is, "Because my instructor taught me to do it that way," then my next question is, "Why did your instructor say that was important?")
Click to expand...

It's part of the checklist in my flightschool for the PA-28 and is taught by the instructors there. The rationale is to ensure that any potential icing of the carb is found and addressed at pattern altitude. Minimizes the potential for icing to cause engine/power issues on base/final or, worse, if we need full power for a go-around. As just one example, there are plenty of deer on or around our runway in the evening and go-arounds (or low flyovers to scare them away) are not uncommon.
 
Ron Levy said:
My experience with Lycoming-powered carbureted 172's is that they are just as resistant to carb ice as the same engines in Piper, Beech, and Grumman airframes, but for reasons understandable only to Cessna (maybe their lawyers :dunno:), the later 172 manuals still call for full carb heat in the landing checklist regardless of conditions.
Click to expand...


My experience with lycoming powered Cessna 172, 177 & 177B is as you describe.

Only time I've ever recognised carb ice, was in a O-300 powered 172H, flying through soup in Seattle
 
I teach use of the carb heat in the carburated PA28s exactly the same as in the C172s, following NTSB Recommendations A-89-140 through -142:

Therefore, the National Transportation Safety Board recommends that the
Federal Aviation Administration:

Amend, as necessary, in conjunction with the General Aviation Manufacturers Association and the airframe manufacturers, the descent and before-landing checklists
in the pilot’s operating handbooks and airplane flight manuals of carburetor-equipped airplanes to require the use of full carburetor heat when engine power is reduced
below the normal cruise power range (the green arc on the tachometer or the manifold pressure gauge), or below an alternate engine power setting as determined by the
manufacturer. (Class 11, Priority Action) (A-89-140)

Emphasize, through its pilot education programs, the potential problem of carburetor icing and steps to preclude its occurrence during the descent phase of flight as outlined in Safety Recommendation A-89-140. (Class 11, Priority Action)(A-89-141)

Revise, as necessary, and distribute Advisory Circular 20-113 on engine induction system icing to all certificated pilots, flight instructors, and flight schools. (Class 11, Priority Action)(A-89-142)
 
JasonM said:
I recently started flying the PA28 and was told on checkout that I did not need carb heat as part of my landing checklist. Is this the norm? I'm just so used to always applying full carb heat when doing my pre-landing checklist.

Is the PA28 less prone to carb ice?
Click to expand...

The National Transportation Safety Board, well aware of possible confusion between different aircraft models/engines and POH procedures, issued a safety notice advising ALL pilots to use FULL carb heat whenever power is reduced below cruise power, no matter what kind of engine or what kind of aircraft. Makes sense to me...adding full carb heat to the landing checklist doesn't hurt anything.

Bob Gardner
 
It's interesting to know that the Cherokees and Lycoming powered 172s don't require carb heat. I was taught from the start to pull carb heat abeam the numbers, just before reducing throttle to near idle, just in case. Every instructor I flew with in both PA28s and 172s expected it, so maybe preferences vary by region. I don't feel the risk in a go-around is much if any higher; it's never been a big factor when I had to go around. So... if there's a carb heat knob present, it gets pulled when I start my descent from the downwind leg.
 
bobmrg said:
The National Transportation Safety Board, well aware of possible confusion between different aircraft models/engines and POH procedures, issued a safety notice advising ALL pilots to use FULL carb heat whenever power is reduced below cruise power, no matter what kind of engine or what kind of aircraft. Makes sense to me...adding full carb heat to the landing checklist doesn't hurt anything.

Bob Gardner
Click to expand...
Perhaps, but it seems a little silly to base a checklist item for ALL carborated airplanes because a single aircraft manufacturer requires it. Or, as I asked earlier, can someone else point to a different manufacturer other than Cessna that requires it?
 
Fearless Tower said:
Perhaps, but it seems a little silly to base a checklist item for ALL carborated airplanes because a single aircraft manufacturer requires it. Or, as I asked earlier, can someone else point to a different manufacturer other than Cessna that requires it?
Click to expand...

The NTSB was concerned about pilots getting confused by conflicting "rules," so they posited a one-size-fits-all solution.

Bob
 
bobmrg said:
The NTSB was concerned about pilots getting confused by conflicting "rules," so they posited a one-size-fits-all solution.
Click to expand...
They could also do something about gear-up landings due to pilot confusion over what type plane they were flying by saying the gear should be left down at all times, too. Personally, I don't think either is an appropriate solution to the problem of pilots not following appropriate procedures for what they're flying.
 
Ron Levy said:
They could also do something about gear-up landings due to pilot confusion over what type plane they were flying by saying the gear should be left down at all times, too. Personally, I don't think either is an appropriate solution to the problem of pilots not following appropriate procedures for what they're flying.
Click to expand...

Or, said another way, pilots not possessing adequate knowledge of the systems for the aircraft that they're flying. Of course, many instructors don't possess that adequate knowledge, either.


JKG
 
Not being aware of which PA-28 model the OP is specifically referencing, I am looking at the POH for a PA-28-16. Manual VB-880. If in that manual you look at section 4.28 Descent and 4.29 Approach and Landing, it addresses the usage of carb heat.
 
murphey said:
It's not being more prone to carb ice, it's a different physical setup firewall forward. In the pa28 the carb is physically located in a different location so that is carb is heated by the engine, thus reducing but not completely eliminating the chance of carb ice.

When in doubt, use carb heat if you are more comfortable but remember to turn it off when you need full,power in a go-around.

In 12 years of owning the cherokee, I think I've used carb heat twice.
Click to expand...

It depends if you have a Continental or Lycoming powered 172. If it's a Lycoming, it's identical to a Cherokee.
 
On my Archer, my CFI insists on me "checking" my carb heat by turning it on for a moment and noting the RPM drop and turning it back off midfield on the downwind leg.

I always thought that was weird since it's not in my checklist and because it doesn't make sense to me that turning it on for 2 seconds would do anything but tell you it works.
 
The way my CFI has me fly the 28-161 is on downwind parallel to touchdown point, carb heat on, rpms @1700, first click of flaps. Not sure which engine we have for sure.

Sent from my SAMSUNG-SM-N900A using Tapatalk
 
jps6882 said:
The way my CFI has me fly the 28-161 is on downwind parallel to touchdown point, carb heat on, rpms @1700, first click of flaps. Not sure which engine we have for sure.

Sent from my SAMSUNG-SM-N900A using Tapatalk
Click to expand...

Lycoming 0-320, you should know that. Out there it's a rare day you'll get carb icing.
 
Jim_R said:
Based on what rationale?
Click to expand...

Because if you have any unnoticed (thus very little) icing, hitting the carb heat will unstick it, where it will be ingested into the engine. This will cause a little roughness for a moment, and you'll know at that point that this might be when "as needed" = "yes" . . .which is something that you want to learn as far away from the ground as possible.
 
Thought I would chime in on this. I think landing is a perfect time to at least check carb heat in any non fuel injected plane. Why you ask? I was flying a 172 with my CFI doing short fields and soft fields one day and I noticed my climb rate sucked ! I mean barely clearing trees by a 100 foot or so at the end of a 5000 foot runway (kthv). I repeatedly told the CFI that I believed carb heat was stuck on and probably had been for a while because I had noticed crappy performance on previous flights but wasnt doing things that would make it stand out so much. We checked on downwind a couple times and lo and behold it was stuck on!

Check it regularly.....that loss of horsepower would have sucked if we had gone to clearview MD 2w2 that day!

Sent from my Nexus 7 using Tapatalk 4
 
I take issue with Lycoming icing being very rare, having experienced it.

1977 Cessna 172N, Lycoming O-320-H2AD. Nice summer day, nearly 70 deg, going up for solo pattern practice during primary training. Marine layer has just cleared and lots of aircraft are queueing up for departure. Do a run-up, then lean and pull to 900 RPM waiting for takeoff sequence. It takes a while. On takeoff, apply full power, full rich (of course), and the aircraft climbs nearly normally (but in retrospect, it was a little weak considering I was solo -- but would have been normal for a larger load). At 400 AGL, the ice breaks clear and the engine ingests it, stumbling. Thinking I lost a mag, I push the nose down intending to set it down in the bayside mudflat, and the aircraft accelerates level. OK, still flying, so I turn crosswind and complete the pattern. Once on the ground, I give it a mag check on the parallel, and it's totally fine. Since it isn't explained at that point, I abort the practice and park the airplane.

Maybe that wasn't carb ice, but conditions for it were absolutely perfect, and symptoms completely consistent.
 
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