Old Wives Tales

USMCmech

USMCmech

Well-Known Member
What are some OWTs that you have heard?

Most of these have been around for ages. They either no longer apply, or were dead wrong in the first place. /ubbthreads/images/graemlins/banghead.gif

"never run your engine oversquare"
Then why do the manufactures have a "oversquare" power setting in their manuals

"stay away from the prop because it might start itself with no warning"
Even if the mag is left on, it won't start without fuel.

"because the FARs say so"
Show me.

"If you run your engine too lean it will explode"
Lean of peak is actually cooler and may be easier on your engine.

"the only safe way to enter a patern is the 45deg on downwind"
The safest way to enter the pattern is the one where everybody else understands where you are at and what you are going to do. If that is a 3 mile final, or a 45 deg downwind so be it.

"you have to replace an engine when it reaches TBO"
Only for comercial operators. Otherwise "if it aint broke, don't fix it"

"Never run a fuel tank dry"
Not both at once! However running a fuel tak dry will do no harm to your engine. It's also a good training tool, let the student cause his own engine failure, and see how he reacts. Don't you forget about it and try this while doing ground ref manuvers! /ubbthreads/images/graemlins/blush.gif

"useing auto gas will destroy your engine, and get you killed"
Most of the small four cylinder aircraft engines will run just fine on 87 unleaded. (The larger six cyl, and turbos need 100LL though.)

"at runup make sure you cycle the prop plenty of times to get all the old oil out"
On single engine airplanes, the prop spring forces all the oil out when you shut down, so there isn't any old oil in the prop hub. For twins, there is only about a cup of oil in there to warm up.

And my all time favorite

"Pitch controlls airspeed, and Power controlls altitude"
This may be a simple way to teach a student how to fly a final approach, but it's dead wrong. They are both interconected, change one, you change the other.

Let's set the record straight. Now that I have my CFI and am going to school for my A&P I have learned that a lot of what my instructors taught me is total BS. /ubbthreads/images/graemlins/banghead.gif

For you students don't try to challange your CFI with what you learn here. /ubbthreads/images/graemlins/argue.gif You'll never convince them that their instructor who taught them might have not known what he was talking about, just "smile and nod"

For you more expeirianced guys, what are some I missed?
 
Do you mean "Old Wise Tales" /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/tongue.gif
 
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Do you mean "Old Wise Tales" /ubbthreads/images/graemlins/confused.gif /ubbthreads/images/graemlins/tongue.gif

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Yeah, no kidding, I thought this was going to be a BS sessions about wives, I was going to get my list out......
 
Let me get this straight. Are you recommending that in a single engine airplane, you would allow the student to intentionally run on one tank until it is empty and let them experience a "real" engine failure?

The pitch for airspeed and power for altitude is a good tool to prepare students for BAI. You are wrong in my opinion about them being interconnected. If you are trimmed for straight and level flight at 120 knots and you take out 5 inches of Manifild pressure you should get a 500 FPM decent, the airpseed should remain constant.

It seems to me that you are disregarding safety in some case, i.e the prop. Sure with mags off and mixture idel cutoff, the chances of you being able to start an engine my moving the prop is slim to none. But if you dont teach students to treat every prop as if it were hot then guess what would happen. You would have a lot of maimed pilots. Please don't confuse things that are designed to promote safety with things that should be disregarded as false truths.
 
Just a couple nit-picks. Most myths have start as truths or have some basis in the truth. Over time they neer get correct and you end up with half-truths more than flat out lies.

For example ...

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"never run your engine oversquare"
Then why do the manufactures have a "oversquare" power setting in their manuals

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Arbitrarily running the engine over square could very well damage the engine. Running the engine oversquare within the parameters ofthe power chart is a) perfectly ok and b) the most fuel efficient manner to fly. But yeah this is the most mis-understood "fable" out there.

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"If you run your engine too lean it will explode"
Lean of peak is actually cooler and may be easier on your engine.

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LoP operations are great for fuel economy. HOWEVER, you need the proper engine monitoring equipment to get everything set up correctly otherwise you can very easily cause damage to the engine. Read Lycoming's "Key Reprints."

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"Never run a fuel tank dry"
Not both at once! However running a fuel tak dry will do no harm to your engine.

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It's not the engine people worry about when running a tank dry. It's the fuel pumps. I don't know enough to say one way or the other (in regards to potential damage to the pumps) but running a tank dry is supposed to harm the fuel pumps because "the fuel helps to lubricate the pump" and running it dry can a) run the pump (albeit for a very brief time) without "lubrication" and b) suck up debris (why "this debris" wouldn't have been sucked up when it was suspended in a body of liquid I dunno) but that's the "fear" related to this OWT.

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"Pitch controlls airspeed, and Power controlls altitude"
This may be a simple way to teach a student how to fly a final approach, but it's dead wrong.

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It's not dead wrong - on final this is the way you fly heavier aircraft. 172s, Cherokees? Nah. But any airplane that requires power on final and you'll find yourself doing this more often than not. But I think it would be better if CFIs taught energy management instead of this or any of the other common "methods."
 
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"useing auto gas will destroy your engine, and get you killed"
Most of the small four cylinder aircraft engines will run just fine on 87 unleaded. (The larger six cyl, and turbos need 100LL though.)

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Sheesh dont bring that one up at Cessnaowner.org or Piperowner.org or you will start the proverbial sh&tstorm. Almost like bringing up PFT here.
 
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Yeah, no kidding, I thought this was going to be a BS sessions about wives, I was going to get my list out......

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Why hesitate? Start a new thread . . . this sounds like it could be hilarious! /ubbthreads/images/graemlins/smirk.gif
 
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If you are trimmed for straight and level flight at 120 knots and you take out 5 inches of Manifild pressure you should get a 500 FPM decent, the airpseed should remain constant.


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This is correct.
 
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Let me get this straight. Are you recommending that in a single engine airplane, you would allow the student to intentionally run on one tank until it is empty and let them experience a "real" engine failure?

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Yep, I've done several times, and it was how I exerianced my first one. Always with plenty of altitude. All on cross countries over good terain. Always having briefed the student about what would happen.

Even though it's been briefed, when it actually happens the student just sits there looking confused for a few seconds. You tell him you know whats wrong, but you want him to figure it out. The student runs the engine failure checklist, 30 seconds after he moves the fuel selector the engine starts right up.

Try it on yourself once.

The fuel pumps are not lubricated by the fuel, and the fuel filter traps any contaminates before they get into your engine. Due to the descent profile and fuel tank design in the C-182 I flew jumpers in the fuel lines would run dry on the way down. After a while I got really good at power off landings and didn't even try to restart the engine utill I was stopped on the runway.



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The pitch for airspeed and power for altitude is a good tool to prepare students for BAI. You are wrong in my opinion about them being interconnected. If you are trimmed for straight and level flight at 120 knots and you take out 5 inches of Manifild pressure you should get a 500 FPM decent, the airpseed should remain constant.

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Lift, Weight, Thrust, and Drag are all interconected. If you change one thing the others compensate to rebalance the forces on the aircraft. The Pitch/Power way of teaching is that you trim for an airspeed. Since the airplane want's to stay at a given airspeed changing the power changes the pitch and the rate of descent.



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It seems to me that you are disregarding safety in some case, i.e the prop. Sure with mags off and mixture idel cutoff, the chances of you being able to start an engine my moving the prop is slim to none. But if you dont teach students to treat every prop as if it were hot then guess what would happen. You would have a lot of maimed pilots. Please don't confuse things that are designed to promote safety with things that should be disregarded as false truths.

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Fire requires Fuel, Air, and Heat. No spark/heat. No fuel/ mixture. Air won't burn by itself. Obviously I teach students a healthy respect for the prop arc, but it will not start by itself.

Ever see some one hand proping an old Cub, they stand right in the prop arc and turn it over 2-3 times. Then the guy outside calls "Brakes, Throttle, Contact" Telling the pilot that he may now hold the brakes, open the thottle & enrich the mixture, & activate the magnetos. Now the engine will start when it is thrown. Then the guy outside carefully steps in and thurns the prop in a motion that has him stepping back at the same time.

Do not ever hand prop a plane unless you know what you are doing & trust the pilot.



Obviously there are exceptions to every rule. My problem with OWTs are that the exceptions are applied to all aircraft wether they apply or not, and are accepted blindly without any understanding to the logic behind them.


Check out John Deakins "Pelicans Perch" colums on AvWeb.This guy has a ton of experiance, and is a heck of a writer.

http://www.avweb.com/news/columns/182146-1.html
 
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"stay away from the prop because it might start itself with no warning"
Even if the mag is left on, it won't start without fuel.

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If there is fuel in the cylinders the engine wont start and stay started, but it may swing the prop around with enough force to do some damage. (I've seen a guy knocked down and have his shoulder dislocated when he grabbed a prop and it fired one cylinder).

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"If you run your engine too lean it will explode"
Lean of peak is actually cooler and may be easier on your engine.

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LOP is good, but only up to a point. If you get more than mild detonation going, thats when the damage can start. Watch the egt's and cht's (on all cylinders) and you'll be ok.

If you run it too lean (and what "too lean" is, is running it beyond safe LoP operations) you can get detonation, and if the cylinders or plugs get hot enough you can get preignition, and then you can get bent rods, destroyed/melted/deformed pistons, and the engine is quite capable of self destruction.

You probably arent likely to see anything spectacular unless you are running forced induction where you can setup a leaner mixture with higher temps and pressures than you could get on a n/a setup.
 
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and the fuel filter traps any contaminates before they get into your engine.

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Yeah, who needs a fuel filter. Just clog it up every other flight..............yeah, that's good. /ubbthreads/images/graemlins/banghead.gif

Everyone, please do yourself a favor and DON'T listen to this guy!! /ubbthreads/images/graemlins/crazy.gif /ubbthreads/images/graemlins/cool.gif I'm not saying everyone should just be a drone and take your CFI's word for everything. Paying attention to that sick feeling in the pit of your stomach doesn't hurt either. /ubbthreads/images/graemlins/smile.gif

What's up man, you get your ticket and you think you know it all now?? Very dangerous mind set. Maybe I'm getting the wrong impression, but the last thing anyone needs is a brand new CFI who's out to re-invent the wheel. Tried and true safety practices have been in place for many decades, and for good reason.
 
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LOP is good, but only up to a point. If you get more than mild detonation going, thats when the damage can start. Watch the egt's and cht's (on all cylinders) and you'll be ok.

If you run it too lean (and what "too lean" is, is running it beyond safe LoP operations) you can get detonation, and if the cylinders or plugs get hot enough you can get preignition, and then you can get bent rods, destroyed/melted/deformed pistons, and the engine is quite capable of self destruction.

You probably arent likely to see anything spectacular unless you are running forced induction where you can setup a leaner mixture with higher temps and pressures than you could get on a n/a setup.

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Detonation is a very real concern, but it is most likey at or near peak EGT/TIT. Useing low octane fuel in engines that require 100LL will allow detonation, espically in turbocharged engines.

Far too many pilots have no clue what is happening inside their engine, and simply follow the OWT's regardless of the facts.

The Piper Malibu was a victim of this. It's engine was designed to be run LOP, and the POH specifically called for LOP operations. But everybody knew that doing this would blow up their engine, so they enrichened their mixture a little bit to smooth things out. This placed the engine in a very high temp/high internal pressure condition, and eventually destroyed it giving the Malibu a bad reputation. If pilots had read the POH and followed it, their engine would have lasted to and past TBO.

If a pilot dosen't want to educate himself on how to properly run his engine, then just run full rich all the time and help the FBOs stay in buisness.

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If there is fuel in the cylinders the engine wont start and stay started, but it may swing the prop around with enough force to do some damage. (I've seen a guy knocked down and have his shoulder dislocated when he grabbed a prop and it fired one cylinder).

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You are corect about an engine kicking over, I've seen it happen too. When it happens it has enough force to break an arm.

So do be careful, but it won't run by itself.
 
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"the only safe way to enter a patern is the 45deg on downwind"

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In England 45 degree entry to downwind is not permitted, as with a low wing aircraft you block off planes turn to downwind - they only allow extended entries. Seems sensible.
 
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"useing auto gas will destroy your engine, and get you killed"
Most of the small four cylinder aircraft engines will run just fine on 87 unleaded. (The larger six cyl, and turbos need 100LL though.)

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Sheesh dont bring that one up at Cessnaowner.org or Piperowner.org or you will start the proverbial sh&tstorm. Almost like bringing up PFT here.

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Just like many OWTs, mogas is greatly misunderstood.

Gasoline is Gasoline. The only diffrence is the antiknock additive. Smaller low compression engines aren't really prone to detonation (it does occure, but is very rare). So 87 octane is just fine in and Contential O-200 or an lycoming O-320.

A TIO-540 is a diffrent matter entirely, running anything besides 100LL would be digging your own grave.

Carefully consider if you want to run the calculated risk of running mogas, but do so inteligently. Running calculated risks is what aviation is all about.

The reason that airports sell only 100LL is that having another type of fuel would be an even bigger pain in the a$$. Engineers are franticly trying to find a way to run aircraft on unleaded fuel, because 100LL will eventually be phased out due to enviromental and logistical concerns.

I just read on AvWeb that the 89 leaded octane used by many calssics has been discontinued.
 
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and the fuel filter traps any contaminates before they get into your engine.

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Yeah, who needs a fuel filter. Just clog it up every other flight..............yeah, that's good. /ubbthreads/images/graemlins/banghead.gif

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What's the big deal, many aircraft engines don't have an oil filter.

Most people change the fuel fileter on their cars every two years, after about a thousand of gallons of realitively filthy auto gas has run through it. 100LL tanks are far more closely inspected than the ones at 7-11.

If you are doing your preflight the same way I do mine, you drain the sumps to check for any sediment. Whatever microscopic matter is suspended in the fuel will be traped in the filter which will be cleaned/inspetced/replaced on every annual or 100 hr.

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Everyone, please do yourself a favor and DON'T listen to this guy!! /ubbthreads/images/graemlins/crazy.gif /ubbthreads/images/graemlins/cool.gif I'm not saying everyone should just be a drone and take your CFI's word for everything. Paying attention to that sick feeling in the pit of your stomach doesn't hurt either. /ubbthreads/images/graemlins/smile.gif

What's up man, you get your ticket and you think you know it all now?? Very dangerous mind set. Maybe I'm getting the wrong impression, but the last thing anyone needs is a brand new CFI who's out to re-invent the wheel. Tried and true safety practices have been in place for many decades, and for good reason.

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I've been around airplanes since I was 3, PPL for 8 years, CFI for 2. I am currantly in A&P school having a blast turning wrenches.

However I do not know it all, or even a much. My purpose in starting this thread was to learn if I am following any OWTs without knowing it. I always follow accepted safety practices unless I don't understand why they are done. When that happens I ask for an explanation, and if all I get is "cause, that's what my CFI, and his CFI said" or "it's always been done that way" then I start digging.

The "modern" aircraft engine is based on 1920s technology (a Harley mechanic will feel right at home), yet there hasn't been a real improvment in design because it does it's job very well. Over that time may myths have developed, some with some basis in fact, most without.

The OWT's I am refering to have been conclusivly disproved by mechanics/enginers/and some common sense, but they still keep circulating. They may apply to a few models, or some extream circumstances, but you need to be able to know the differance.


Wow, it looks like I just started my first flame war! Where's my bunker gear? /ubbthreads/images/graemlins/cool.gif
 
No flame war man. I just think you should be careful when you start sharing this kind of information. For the same reasons Preparation H tubes have a printed warning stating: "...do not take internally, for external use only..." Don't ask how I know that. /ubbthreads/images/graemlins/banghead.gif /ubbthreads/images/graemlins/grin.gif
 
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In England 45 degree entry to downwind is not permitted, as with a low wing aircraft you block off planes turn to downwind - they only allow extended entries. Seems sensible.

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That's why I try to stay away from overhead 45 deg pattern entries. My instructor for CFI insisted on them, but everytime I did one I lost sight of all the planes on downwind. This made me really nervous.

So now I teach students to make the pattern entry that is the simplest, and most easily understood by the other planes in the area. If this will result in cutting another plane off, then they should break off or circle as a courtsey.
 
Isn't the safest way to enter downwind is to make a midfield crosswind and then turn left to downwind.

I suppose in a high wing at right turn from the fourty five would be safest as the wing wouldn't block any planes.

Tom
 
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Isn't the safest way to enter downwind is to make a midfield crosswind and then turn left to downwind.

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That's the way I do it, but my instructor for CFI insisted that you come in over midfield at 1500 AGL and make a teardrop entry descending into pattern altitude.

Everytime I did it I was very nervous because I would always lose sight of every plane in the pattern. Which is important when you are trying to slide in between two airplanes.
 
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