What's under the hood

[brien23]

As a IA at a flight school I have been asked to take the cowling off a engine and explain to a ground school class the aircraft engine. Question is what should I spend time on, somethings would be over most in the class to understand and I do not want to underestimate them. So has anyone done this before and what or how in depth did you go, the aircraft would be a C-172M.

 

[Radar Contact]

Explain the flow of cooling air, show spark plugs on top/bottom, show explain mags, show explain induction system, fuel injection/carb, oil cooler/system, baffles/how they work, vacuum pumps, starter, etc. I’d aim small in today’s world and those that are mechanically inclined will probably still appreciate it. I’d think a good summary maybe 20-30 min and 30 of Q and A?

 

[wilkersk]

Dip stick - don't over tighten
checking oil - when and how (cold oil climbs the stick)
Primer circuit - show & contrast with what pumping the throttle does
Identify and briefly describe: alternator, starter/starter ring, magnetos (show them the P-lead and tell them how it works), exhaust, carb heat/alt air, air filter, sump, intake,
If really want bonus points, pull the top plugs and let each one stick their thumb over a spark plug hole and show them the combustion stroke on each cylinder as you describe the firing order.

 

[Briar Rabbit]

The above are good, I would briefly discuss the differences of air cooled aircraft engines vs water cooled auto engines. You might point out that birds are prone to building nests inside the cowling. For example the Cardinal RG has the oil cooler behind the last cylinder on the pilot’s side and below the top of the fins where they can build a nest out of sight. And they can do it in just a day or two. (Went on a cross country and when returning found bird poop on the prop, could not see a nest but to be sure pulled the cowling and the oil cooler was completely covered.) Discuss benefits of cowl plugs. Explain how electric case heaters work in the wintertime and wrapping the cowling with a blanket will help reduce heat loss. Avgas does not atomize as easy as auto gas and the engine may not start in below freezing weather. Plus most air cooled engines do not warm the oil adequately before takeoff unless preheated.

Expand on Kevin’s suggestion about baffles to explain the need to check that their seals are intact so the engine cools properly.

 

[weilke]

Don't assume that they know what you knew about internal combustion engines when you were their age.

 

[Jim Carpenter]

Everyone above has the elements pretty well-covered. Definitely demonstrate carb heat operation, point out primer lines, p-leads, gascolator drain......anything with a handle or knob that is operated by the pilot, the visuals of seeing what physicaally occurs seem to help student understanding.

 

[Bell206]

So has anyone done this before and what or how in depth did you go,

In the past I have used a mx based list as a guide like 43 Appx D or MM inspect form for the area(s) and explained the individual parts, their function if applicable, and showed them what I would look for as a mechanic. The latter part seemed to hold their attention better. If time permitting, would also explain the effects of common "induced" abuses by the operator and how/what part(s) it affects the engine or other items.

 

[Low Level Flyer]

Some good ideas above. Our school has some old pistons, cylinders and a crankshaft laying around. I use those during my ground school on engine systems to help students visualize what’s happening inside the engine.

 

[Brad W]

Yeah, I think I'd focus on typical preflight stuff, common stupid-pilot tricks to avoid, and just a bit on how it works.

Mostly I think these sorts of opportunities are great for them to be able to see more than what their instructor will show and do peering through the dip stick hatch and the little cooling openings for preflight. I'd consider that most PPL students or even licensed pilots who are solely renters (not owners) have never or only rarely ever had a chance to see what's inside the cowling.....so I see it as an opportunity for them to see and touch things that might bring questions to their minds to ask you.