Cherokee 140 pushing the limits

side question.... how many of you aircraft owners have a set of scales in your hangar?
With technology being what it is now, I've got to believe it's not too far fetched to be able to have affordable scales so you can load your aircraft and get an honest "right now" weight and balance....without all of this estimating and ciphering....and not knowing what all sort of stuff has drifted into the map pockets and under the floor boards and carpets over the years....
I now the performance charts and specs for these old birds aren't that precise, safety factors, and all of that....but I do know that if you ask any person their weight they are very likely to give you a number 5-10 pounds or more off....and that's if they are being honest! If you're right on the edge...are you really?


and in response to albany tom's last post.... which makes some excellent points!
I'll venture a guess that any student that has flown a cessna 150 with a male CFI in their primary training has likely flown OVER max gross at least at some point.
 
Do a test flight or two on a long runway with the aircraft ballasted at the weight you're planning on for your trip. See if it makes numbers (or what numbers it does make) at the weights you're considering.
 
Seems like we say we’re taking about WB (weight and balance) but only actually talking about W. Ferry pilots routinely go well over W but are very sensitive to B.

Cherokees are very forgiving for B (i.e. have a broad range; NOT the same as saying they fly OK outside the range) but you should just double-check; the plan you have should keep it squarely in the envelope but if you do some other flight with heavy stuff in the baggage area it could be different.

W tends to influence takeoff roll. B tends to influence handling and stability in the air.
 
Brad W said:
side question.... how many of you aircraft owners have a set of scales in your hangar?
With technology being what it is now, I've got to believe it's not too far fetched to be able to have affordable scales so you can load your aircraft and get an honest "right now" weight and balance....without all of this estimating and ciphering....and not knowing what all sort of stuff has drifted into the map pockets and under the floor boards and carpets over the years....
I now the performance charts and specs for these old birds aren't that precise, safety factors, and all of that....but I do know that if you ask any person their weight they are very likely to give you a number 5-10 pounds or more off....and that's if they are being honest! If you're right on the edge...are you really?


and in response to albany tom's last post.... which makes some excellent points!
I'll venture a guess that any student that has flown a cessna 150 with a male CFI in their primary training has likely flown OVER max gross at least at some point.
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Don’t have. But did when I had a plane and hangar.
 
MBDiagMan said:
This thread keeps ringing, or maybe gonging, in my mind. Thinking about planning down to the minute and cutting onboard fuel to a thin margin is troubling to me. Here’s why it rings in my head:

About three years or so ago, I agreed to fly to the Houston area to pick up my son in law because he was leaving his Baron B58 for some major avionics and interior retrofit. About two days before we made the trip, it was in the news that a B58 had gone down at Kerrville, Tx killing all aboard. The Baron was owned and flown by a Houston area ATP rated pilot who just enjoyed flying and was always quick to offer rides because he enjoyed flying.

My SIL was a little upset over hearing of the accident involving people he didn’t know, maybe because it was in a plane very much the same as his. I could tell by the way he talked about it that the accident had gotten his attention and he was wanting to learn more about the circumstances.

When my SIL and I made the trip, he got away a little earlier than me and could of course outrun my Mooney, I got there, taxied in and found my SIL in the shop owners office in the midst of a somber conversation. It turned out that the shop owner, the downed pilot and the local Beech representative were all very close friends. The shop owner said that the pilot had loaded the plane to the max and fueled enough for the trip. They ended up in IMC and an unexpected wind change that caused them to have to pass the airport to shoot the approach from the opposite direction rather than going straight in. They ran out of fuel on the approach, during the reversal leading to the approach as I recall, and for whatever reason, the plane went down flat. All passengers remained in their seats after slamming into the ground. There was no fire. Tanks were bone dry.

The shop owner said that his friend the Beech Rep had been very upset and was saying something to the effect that the plane would have flown heavy, but he should have carried enough fuel. You have to have fuel!

Obviously the best decision would have been to reduce weight AND carry adequate fuel margin, but you MUST HAVE FUEL!

Even on a beautiful VMC day with no clouds in the forecast for the next week, that flight can hold unexpected events. Don’t scrimp on fuel! Have enough fuel and plenty of reserve for the trip even if you have to leave baggage on the tarmac.

Flying is SERIOUS life and death, unforgiving business. Take it seriously.

My $0.02,
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I believe there is an AOPA safety video about this Houston flight available on YouTube. The pilot was experienced - 3300+ hours and he didn't have enough fuel for sudden weather changes and a missed approach. Very sobering….
 
I have flown 150 pounds under gross in the Cherokee and within balance more towards the nose but still within the envelope. With the load I will have balance is right in the middle so balance is not an issue with weight just under max. Given the W&B was done 5 years ago right after I acquired the plane it is more accurate than the factory W&B. I also weighed everything in the baggage compartment which is about 17 pounds (oil, tools, cowl plugs, chocks, cushions, headsets). One thing I have not done is verified how close performance matches the POH. Since I have lots of fuel to burn before I do this I will take another pilot with me and observe the takeoff distance and climb over 50 foot obstacle and compare to the POH.

I started flight training in a 152 with full fuel and never had an issue. I was 170 at the time and my male instructor was no more than 5’ and thin. When he went out on a medical issue and handed me off to another instructor we switched to a 172 due to weight. I understood that reason at the time and going back and calculating weight alone for the 152 we would only be able to carry around 10 gallons. Not enough to get up, fly to the practice area and back without time inbetwen for anything instructive.
 
RonP said:
I am planning a flight that will max out my airplane. I am looking for opinions as I have never flown it at max TOW and less than half tanks of fuel. It is a 1969 Cherokee 140B stock except for the following:

  • climb prop instead of the stock prop
  • LED landing light
  • uAvionics SKYBeacon

I had a W&B done 5 years ago. I am planning a 36 minute flight from south ‘Jersey from 17N (162’ MSL) to KWWD (Cape May 22’ MSL) with 4 adults. Per the W&B I will be at max TOW (2,150lbs) with 20 gallons of fuel of which 18 is useable. Per the performance charts with a density altitude on a hot day of 2,000 feet I need 2,150’ to clear a 50 foot obstacle (maybe less climbing at Vx 75mph) to clear trees at the end of the 3,500 foot runway. I should be able to make it to Cape May and back with the 20 gallon fuel on board or even top off to 20 gallons before leaving Cape May. I know the climb will be anemic but the numbers show this is within performance limits. I have heard tales of the 140 not being a 4 adult airplane with disastrous results. The adults are not big people with me at 175lbs, right seat person at 152lbs and 2 small women in the back seat at 120lbs and 156lbs. Am I looking to be another aviation related statistic or safe to make the trip?
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i have done this at gross weight in an ancient 150hp cherokee on a 2000’ DA day and i started at about 100’ per minute climb. Took about 90 minutes to get to 4000’. A bad downdraft or engine hiccup and we would have been f’ed. although it was texas gulf coast and weather was pretty stable - just hot as ****.
 
Old97 said:
i have done this at gross weight in an ancient 150hp cherokee on a 2000’ DA day and i started at about 100’ per minute climb. Took about 90 minutes to get to 4000’. A bad downdraft or engine hiccup and we would have been f’ed. although it was texas gulf coast and weather was pretty stable - just hot as ****.
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You have my attention! Something is off here with the POH or the airplane. Per the POH the climb at 2,000’ DA should have been 600 FPM. To take 90 minutes to get to 4,000’ is a climb rate of 44FPM. Even at a DA of 4,000’ the POH states climb should be 500FPM. I understand the POH can be off some as well as changes in the airplane and engine over time but to get 44FPM climb just doesn’t sound right. Am I missing something or can the POH be that grossly incorrect?
 
RonP said:
You have my attention! Something is off here with the POH or the airplane. Per the POH the climb at 2,000’ DA should have been 600 FPM. To take 90 minutes to get to 4,000’ is a climb rate of 44FPM. Even at a DA of 4,000’ the POH states climb should be 500FPM. I understand the POH can be off some as well as changes in the airplane and engine over time but to get 44FPM climb just doesn’t sound right. Am I missing something or can the POH be that grossly incorrect?
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the plane was probably not conforming perfect to the as-new condition the manual was written about. And not surprisingly we weren’t at WOT all the way to 4k.
 
Old97 said:
the plane was probably not conforming perfect to the as-new condition the manual was written about. And not surprisingly we weren’t at WOT all the way to 4k.
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I appreciate the concern about an anemic climb of 90 minutes to 4,000 feet (approx 44FPM). However not climbing at WOT does not imply the POH is wrong, the engine not performing as new nor the airframe. I would say any airplane at a throttle setting other than WOT will not climb per the POH even when new. Is there a reason you chose not to climb at WOT such as not overheating the engine? The only climb parameters I am aware of in the POH are WOT at Vx, Vy and recommended cruise climb speed which is still at WOT but a higher speed and less AOA to allow more cooling air to get to the engine. My preference is to get as much altitude as possible using Vx, Vy or cruise climb speed so I have a greater glide distance if there is an engine issue. Is there a valid reason to not climb at WOT in a carbeurated fixed pitch piston engine?
 
If the airplane is mechanically airworthy, there should be very little performance degradation over a new airplane. Poor performance can usually be attributed to poor maintenance and airmanship.

Weight and balance might be way off, especially weight, with the owner having lots of needless junk in the airplane but making his gross weight calculations based on the last W&B paperwork.

The engine might not be up to snuff, and sometimes that's due to poorly-maintained magnetos and sparkplugs, sometimes carbs, sometimes ignition harness. Sometimes it's a propeller that has been dressed incorrectly and too many times, and it just doesn't make much thrust anymore. There are specified limits for width and thickness of the prop blades at various stations along the blade, and there are specified airfoil profiles that must be maintained while dressing. I've seen props way out of limits on both of those.

The airplane's Type Certificate Data Sheet has critical details. An excerpt from the Cherokee 140's:

upload_2022-6-18_18-22-57.png

Look at those RPM numbers. That's with the brakes locked, and the engine at full throttle, no wind, standard day or reasonably close to it. Too much RPM usually means that prop isn't loading up anymore, or the tach is shot. Too little means the engine is half dead, or the tach is shot. And the low RPM could be due to weak spark (several causes for that): ignition timing off, carb worn out, leaking induction manifold, muffler having loose baffles block the outlet. Ignition timing is the biggest culprit, weak spark next.

The airplane's flight controls might be misrigged and offering extra drag.

The pitot-static system might have leaks that cause airspeed errors, and the pilot ends up flying at the wrong climb speed, costing climb rate.

Lots of stuff. Annuals are supposed to check all this stuff, but I have found way too many airplanes that look as if the mechanic did a walkaround and signed off the logs. Lots of stuff that has been way off for a long, long time and nobody corrected it, probably because they never looked for it.
 
RonP said:
You have my attention! Something is off here with the POH or the airplane. Per the POH the climb at 2,000’ DA should have been 600 FPM. To take 90 minutes to get to 4,000’ is a climb rate of 44FPM. Even at a DA of 4,000’ the POH states climb should be 500FPM. I understand the POH can be off some as well as changes in the airplane and engine over time but to get 44FPM climb just doesn’t sound right. Am I missing something or can the POH be that grossly incorrect?
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It isn't that it's grossly incorrect. It's that it's correct for a relatively new airplane and a new engine, with 0 safety margin. People quoting 1970's PA-28 manuals like there's some science behind them is, to me, nuts. 2000' DA and a 44 FPM climb, full gross, to me sounds like a tired engine. But I've never been in a stock -150 that would do 600 fpm at full gross and 2k, either. A -180 will, with a good engine.

It's appropriate to use the performance charts to COMPARE to your own aircraft, so that you can compare your actual values to the predicted book numbers, interpolate predicted values for different situations, and then add a safety margin. I wouldn't extrapolate, either for weight or DA.

Or in other words....if the numbers tell you can't do it, then it's impossible. Not unlikely, but impossible. You need to determine what percentage, or altitude, or weight or length you are below predicted for the ideal aircraft that maybe never existed. This is all my opinion, flying pa-28's of various flavors out of a field where from time to time pilots walk in with little bit of tree branch they pulled out of the gear from a takeoff or landing.
 
A Cherokee with 150 HP climbing at 100 ft/m at 2000 ft DA while being within W&B? No way unless something was majorly wrong with the plane or you were way above MTOW due to junk in the plane that wasn't accounted for. My home field is right about 2000 ft. I routinely see 3-4000 ft DA and even when fully loaded, I easily get 400 ft/m initially. Granted, I have 160 HP but I doubt those 10 extra horses would make that much of a difference. Heck, even my tired, way past TBO Cessna 150 climbed better than 100 ft/m fully loaded at 2000 ft DA.
 
Dan Gordon said:
I believe there is an AOPA safety video about this Houston flight available on YouTube. The pilot was experienced - 3300+ hours and he didn't have enough fuel for sudden weather changes and a missed approach. Very sobering….
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Thanks Dan! I didn’t know that a feature on the accident had been issued. I would recommend it as a worthwhile view for any pilot:

 
I used to rent a Cherokee 140. It was the Piper I learned to fly Pipers on. It really flew great, for as little power as it had. It's light. It was just an all around, fun airplane. The first airplane I owned was a Turbo Arrow. I mean all airplanes are fun to fly, but the TA was less fun to fly than the 140. Especially when the threat of oil exhaustion and turbocharger failure in flight looms over you (both nearly happened to me.) And it was heavy. The Arrow II I bought in to was a fresh breath of air. It flew just like the 140 I used to rent. Except you could pick your feet up.
 
Chrisgoesflying said:
I doubt those 10 extra horses would make that much of a difference.
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Even 10 extra hp on takeoff will make an enormous difference in climb rate, because climb is directly related to EXCESS power over that needed for level flight. Those extra 10 hp are likely to be a large fraction of the excess power needed for climb. When I converted my 150 hp engine to "160 hp" by installing high compression pistons via STC, takeoff climb rate increased by several hundred fpm. For similar reasoning, an engine that is a few hp shy of expected power might experience a significantly more anemic climb rate.
 
chemgeek said:
Even 10 extra hp on takeoff will make an enormous difference in climb rate, because climb is directly related to EXCESS power over that needed for level flight. Those extra 10 hp are likely to be a large fraction of the excess power needed for climb. When I converted my 150 hp engine to "160 hp" by installing high compression pistons via STC, takeoff climb rate increased by several hundred fpm. For similar reasoning, an engine that is a few hp shy of expected power might experience a significantly more anemic climb rate.
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If the engine is not performing properly wouldn’t that show up not being able to be within the static RPM range? Even if the engine is worn if the propellor is spinning at the correct static RPM wouldn’t the power at the prop be the same as a healthy engine? I would suspect a worn engine putting out less power would not be able to spin the prop at the proper static RPM. Can that be a valid indication the engine is not putting out full power? Wouldn’t that also be an indicator of a worn engine when starting the takeoff roll that the RPM is not up to standards and the takeoff should be aborted?
 
I think that's a good indicator, to see if your aircraft engine is normal before takeoff. But I don't think it's a valid comparison between two different aircraft...unless the RPM is low. Or in other words, I wouldn't just depend on static speed to qualify a different plane.
 
The static RPM range is given to allow to determine engine health. But it also depends on the propeller being the correct model as stated in the TCDS. Aircraft that list several prop models will have Static RPMs given for each prop.

An engine has to be pretty badly worn out to miss the mark on that test. The compression would have to be really low. Or the cam badly worn so valves aren't opening all the way. Or the engine controls are so badly misrigged that the throttle isn't opening all the way, or the carb heat is partly on, or the mixture setting is way too rich, or the prop control has the governor increasing prop pitch when it's not supposed to be. Like I said, more often it's weak and maladjusted magnetos, or stupid spark plugs.

Aircraft are supposed to meet Type Design to remain airworthy. That's what Continued Airworthiness is all about. Unfortunately, based on what I've seen, a lot of airplanes get pencil-whipped annuals, and so many defects are missed or ignored and performance suffers as a result. These things aren't supposed to get old and feeble and shaky like a human body does as it ages. If they do, they're not being maintained. Period.
 
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