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[Habu]

Leaning is good. But you have to be careful to avoid engine damage. Running 50 degrees rich of peak on the EGT is actually the worst temp you can select as that gives you the highest cylinder head temps. Never run your engine with a cylinderhead temp more than 375 for an extended period of time.

I bought a JPI engine monitor for my 182 and on my recent flight to Florida I was leaning very aggresively. It is called running lean of peak as you pull the mixture back so far the EGT's actually start to go down again.

What I found was that I would pull the mixture back until the engine started to run rough then give it a bit more fuel. The cylinder head temps were all 340 or less. I have a carburated engine and I found a bit of carb heat got the cylinderhead temps all very uniform. I had one cylinder that always ran a bit cold for some reason.

EGT was 1550 and I was running 20 inches of manifold. With this setting I was getting 11.5 gallons per hour. Not bad for a big 6 cylinder engine.

World of caution. If you lean aggressively like this never do it in a climb or when running full throttle or if you cannot monitor cylinder head temps. It is possible to burn holes in your cylinders if you get the wrong setting at full power.

[eagl]

The technique I was taught was to slowly pull the mixture until RPMs dropped, then push it back in until the engine smooths out and rpm goes back to normal, then in just a tiny bit more.  And yes, both throttle and mixture full fwd to climb, and mixture in for descents too, otherwise you risk forgetting to change the mixture and the motor might up and quit when you throttle up to level off or go around on an approach.  Tha's wha we call "bad", m-kay...

Carb heat on descents too.  And after my one carb heat incident, I began checking it not only during the pre-flight runup, but also before descents.  If it checked bad inflight before a descent, I knew to keep the power up a bit and just S-turn if I needed to keep speed under control or descent quicker.  Flopping around and flying at the top of the yellow arc is usually better than losing an engine to carb ice

Metallic crystalization was also a big topic back then, so all the fast piston planes were getting speedbrakes installed so you could make faster descents without chopping the throttle to idle.  It was reported that if you made an idle descent, the extra hot-cold-hot heat cycle would increase metal crystallization leading to premature engine wear or failure.  With speedbrakes, you could leave the power up enough to keep the engine warm as you descended.  I never flew planes that were fast enough for it to matter, but being a kid I just pretended it was important and I always made my enroute descents at 50% throttle and somewhere between maneuvering speed and Vne.  If it got bumpy, I'd slow down a bit but darned if I was gonna shock cool that 152 engine!

Most of the other club renters just tooled around at full throttle and chopped to idle for the quickest descents from cruise altitude because the owners charged according to hobbes time, not tach time.  I'm sure that was real good for the engine and plane, but most guys didn't care.  Like when I aileron-rolled a club 172 and killed the attitude gyro (oops).  I think it recovered after fully spinning down, but it wouldn't re-cage after an hour long lunch and another 1.2 hour flight back home.  I never found out because I skipped town and haven't been back.  I still feel bad about that, but at the time that gyro cost more than my car and even if I'd fessed up I couldn't have paid for it.  They never came after me or my Dad even though they knew who rented it that day, so I think it was ok.

[Habu]

Whats it like to aileron roll a 172?

I would never roll my Cessna but wondered what it would do if it was upset in a thunder cloud or something like that.

[Golfer]

I ruined a perfectly good attitude indicator just recently.  My buddy and I were to test fly one of the traffic airplanes (I just tagged along to give a little 'dual' and keep fattening that logbook) and it wound up into a spin training lesson.

I'd been playing with an idea in my head about how to get a spin started in a 172 that I'd "accidently" discovered while learning some basic aerobatics in a 152 Aerobat.  I pitched into a nose down attitude to bump up the airspeed, pitched up to around 30º and just as the airplane was approaching stall I went full left rudder, aileron and gave a tug of elevator to load up the wings.  The low wing stalled, the high one kept flying and the next thing ya know we're inverted roughly 60º nose down with the engine spinning 2400rpm. (the nose was DOWN there baby!)  I kept the spin inputs in and it went right into a spin from that attitude and let it go for three turns, came back on the power and recovered.  172 Spin recovery is simply opposite rudder.  When we came out of it, he looked at me and asked if we were upside down...I replied to the affirmative and he was all grins.  Just after being cleared to land while on a 2 mile base, I noticed that the attitude indicator wasn't indicating what was really going on.  If we were in a 30º left turn it would have been right on, eh...oh well.  After a discussion that consisted of "it happened in flight...right?" we landed and put it in the squawk book.

Oopsie!

[eagl]

The big trick in aileron rolling a 172 is that you really need to pay attention to the speed and engine rpm because as you roll over, the nose will drop.  It doesn't just drop, it plummets.  I started between 20 and 30 degrees nose high, and with full aileron and 1/4 rudder deflection, we still finished the roll about 35 deg nose low.

I started with about 120 mph, used 1.5 G's in the pull up, about .8 G's during the roll to slow the nose drop while inverted, and pulled 2.5-3 G's pulling back up.  I came close to overspeeding the engine because I hadn't cut the throttle as the nose dropped, but I managed to keep it a couple hundred or so rpm below redline.  We never exceeded maneuvering speed too.

In short, it rolled like a pig but it can be done.  Again, the trick is to start out nose-high enough that you sort of make this big ballistic arc as it slowly rolls around, and watch the rpm and speed in the second half of the roll when the nose falls below the horizon.  I'm sure you could prevent the nose from falling as much by using various rudder and elevator inputs to help keep the nose up a bit, but that would be very uncomfortable and you'd risk screwing it up bad and overspeeding something.

I've done it once and don't feel the need to do it again.  It wasn't all that exciting but my Dad had never done one and I'd just finished UPT, and there we were at 6500ish ft over the acro practice area near Ramona, so...

edit - I forgot to mention that although I'm not an expert on the FARs and AIMs, it may have been illegal to roll that sucker.  The nice thing about the aviation regulations is that you can pretty much do anything you want as long as you only kill yourself, so if you fly acro in a private aircraft, you're really just transitioning to the "utility" rules which are sometimes (used to be?) just the normal rules without as much margin for safety.  But I really don't remember if we were legal at the time.  We were in uncontrolled airspace and in an area commonly used for acro practice, but I don't remember the restrictions on using that plane in the utility category.  I don't think chute wear was an issue.  I've had 3 acro flights in private/civilian aircraft and never wore a chute.  2 of those flights were in privately owned homebuilt biplanes though, so again I'm not sure what rules we were operating under.

[CyranoAH]

Performing pseudo-aerobatics in utility aircraft is just asking for trouble, just my opinion...

If you want to fly aerobatic, do it properly, and always wear a chute.

Daniel

[Maverick]

Originally posted by CyranoAH
Performing pseudo-aerobatics in utility aircraft is just asking for trouble, just my opinion...

If you want to fly aerobatic, do it properly, and always wear a chute.

Daniel

Got to agree with that statement. If it isn't rated for aerobatics don't do them.

[bunch]

The POH will tell you what manuvers are safe...My 172n POH says in the utility category Chandelles, Lazy 8s, Steep turns, spins & stalls are all OK & it gives some restrictions on the performance of them

[eagl]

I wonder if HT wears a chute

As for asking for trouble, I try to take the Bob Hoover approach...  Don't try anything you're not capable of pulling off, and leave a margin for error until you're SURE you got it right.  So far it's worked for me.

[CyranoAH]

Originally posted by eagl
I wonder if HT wears a chute

As for asking for trouble, I try to take the Bob Hoover approach...  Don't try anything you're not capable of pulling off, and leave a margin for error until you're SURE you got it right.  So far it's worked for me.

That's quite ok, but that means you are completely sure about what you can pull off and what the plane can pull off... and that's some assuming...

I was talking to Vytautas Lapenas, the Lithuanian who trains the spanish aerobatic team, and asked him about a particular stunt that I saw: two consecutive cobras after take-off.

He said most unlimited aerobatic planes could pull it off, but asked me "unless you earn your living from airshows, why risk it?". Just a slight engine problem means you're done...

Even when you know you can do it, and you are pretty sure the plane can do it, ask if it's worth it.

FWIW, when we train, we only leave a 10-second margin in which we are sold, and that is right after take off. After those 10 seconds, we are flying high enough to make an emergency landing at the airfield.

The rest of the flight, we fly in the box, and even the approach after the aerobatics are over is planned so that in case of engine failure, you get plenty of time to make it to the runway. Engine remains at 60-70% until we are lined up with the runway at the right altitude and speed. Then we cut the throttle and slip to the runway. If the engine fails, we land on the runway anyway.

That way, the only accidents that we risk are while ferrying the planes to other airfields for competitions.

I'm pretty sure these procedures are shared by most aerobatic teams around the world.

Daniel

[eagl]

There's always the unknown risks, no matter how safe you fly.  It's all about risk assessment and risk management.

[Chairboy]

I was hoping to get enough flying in the Cessna in this week so I could take my three year old up this weekend (he's desperate to fly flying), but I've been called to LA on short notice for business.  

Ah well.  I've reserved the plane I trained in for a flight on Thursday evening, I think I'll go up with a friend of mine instead.  Should be interesting to go back to the Cherokee!

[CyranoAH]

Originally posted by eagl
There's always the unknown risks, no matter how safe you fly.  It's all about risk assessment and risk management.

My point exactly. What I'm saying is that one should always think twice about risking it without the proper equipment.

Daniel