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I just watched a video about the traffic pattern. In the comment section below, the uploader spoke about touch & go's:

I don't like to do touch and go's, as a student pilot I used to do them cause you saved money, but its not worth it. Always better to get off the runway, let the engine stabilize**, and then set up properly for the next flight/takeoff.

** by stabilize I mean let the engine warm up under its own power on the ground, because the engine was just at idle or low power for a while during a landing, with the air flow turning the prop and cooling it, and abrupt power-up for a takeoff can "shock" it, that is when usually engines fail.

Dont get me wrong, I'll do a go-around in a second and engines are tough and this does not happen often, but the bigger the engine, the less you want to do that. Some flight schools even forbid touch & go's now.

By GVad The Pilot. Video Link.

  • Is it really bad to make touch & go's for the engine?
  • Do some flight schools really forbid touch & go's?
  • Are his concerns reasonable?
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    $\begingroup$ No. Touch and gos are fine. You can do touch and gos every day all day without hurting anything. I point to millions of hours flown on the GA training fleet and the average actual tbo of a flight school's trainers. The school I worked for used autogas and flew over 3000 on many of their engines. They were not unique. The idea that the engine sees some kind of benefit from "stabilizing" is questionable (would like to see data) and the idea that the engine is somehow "shocked" is nonsense. $\endgroup$ – acpilot May 21 '17 at 14:09
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    $\begingroup$ Related $\endgroup$ – Pondlife May 21 '17 at 14:17
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    $\begingroup$ I'd question the uploader's belief that the engine even needs to "stabilize" after approach. I don't have any metallurgy-based reasons for believing this; just the fact that I've flown many airplanes that were doing touch-and-goes before I was even born and still didn't have so much as a hiccup when I was doing them myself. That said, most of the other responses have pointed to the fact that a full-stop landing does teach better piloting skills than t&gs do. But sometimes it's not the proper time to reinforce those skills; thus touch and goes. $\endgroup$ – Shawn May 22 '17 at 17:40
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As an automotive engine mechanic with 35 years of performance oriented experience and 29 years of that with ASE Master Certification and about a dozen other engine specific certifications. Twenty or so years ago I trained to be a piston engine aviation tech. So I think I can say with some certainty that I know a thing or three about how engines work and what sort of things can have a detrimental effect on them. "Thermal shock" is definitely bad for an internal combustion engine. That said, touch & go's will not cause thermal shock to occur in a piston engine, here's why. Thermal shock is what significantly rapid and drastically uneven temperature change in an engine is called. This means if one or the other isn't occurring then there's no thermal shock occurring.

(To be accurate, it's more a degree of severity, as these conditions happen during normal operation and always will.) The minimum operating temperature called for by the engine manufacturer is to avoid thermal shock. It is important enough for the manufacturer to stress because it is the only reasonable condition the pilot can produce enough thermal shock to damage the engine. When the engine is below the minimum, applying full power causes the pistons and rings to heat up and expand much more rapidly than the cylinders. This in turn reduces the clearance around the pistons and can dramatically increase the friction. The increased friction compounds the problem by adding to the heat and expansion of the piston. More expansion -> more friction -> more heat... This quickly becomes a deadly self reinforcing loop. Because the pistons can't shed heat to the cylinders fast enough the cylinders don't expand and very quickly there's no clearance and the piston seizes up inside the cylinders.
Rapid temperature change in part of the engine without a matching change in the rest. This is the part of thermal expansion that breaks things. The piston to cylinder heat transfer is very inefficient. But the transfer of heat, to the air from the engine, is even slower. So, once the engine is warmed up, it stays that way till it's parked in the hangar and you're headed out. That's just physics 101.

The alternative situation is not likely to happen and if it did, your last worry would be the thermal shock to your engine as the engine wouldn't be running long enough to get damaged, from heat shock that is. What I'm talking about is full submersion of the engine in water. Given this scenario I am doubtful "thermal shock" would really be on your mind. To be honest, I'm not sure if even the coldest water you could keep liquid is cold enough to chill the cylinders to the point of interference.

The belief that touch & go's cause too much "thermal shock" probably comes from mechanics understanding the cumulative effect of dissimilar thermal expansion caused by repeated full throttle application during the touch & go's, but being unwilling or unable to explain that it is really only an issue during the run-in period of time when the new rings are seating in freshly honed cylinders.

The only other way I can see touch & go's being an issue is if a freshly built engine is put together with too little clearance between the pistons and the cylinders. In the extreme, repeatedly heat stressing the engine could scuff its way to a seized piston. None the less, that wouldn't be thermal shock anyway. That would be builder error and the probable source of stories that say "Touch & go's will blow your engine up!"

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Is it really bad to make touch & go's for the engine?

Generally speaking, no. First off "shocking" an engine is generally referred to in the context of cooling it not heating it. For what its worth the consensus is that this is largely an academic debate anyway and may or may not actually contribute to engine wear. There is some logic that dictates that cold oil does not lubricate as well as hot oil but if the engine is running (even at idle) the oil is generally hot enough to lubricate properly. In this case the engine would have been warmed up, at first start the oil may be cold. According to continental the minimum oil temp for takeoff is 75F

Oil Temperature Limits

  • Minimum for Take-Off .... 75°F.

On your average spring/summer day that may very well be ambient air temp. But we can take a look at their cold weather procedure (below 32 F ambient air temp on the ground) for the really cold situation,

  1. When the oil temperature has reached 100°F. and oil pressure does not exceed 80 psi at 1700 RPM, the engine has been warmed sufficiently to accept full rated power.

So as long as your gauges are reading within those limits on approach I see no reason a go around would be any problem.

Please note the above listed info is for one make and model of continental engine and you should always consult your aircraft's POH for the numbers relative to your aircraft's configuration.

On a bit of a related note, when doing a touch and go you should apply throttle smoothly and not just slam it forward.


Do some flight schools really forbid touch & go's?

Not that I have ever heard of but some airports do (usually as a noise abatement thing) so it may just be that the flight school in question does because the airport does. That being said the planes generally belong to the flight school, they can make what ever rules they so please.


Are his concerns reasonable?

Eh, depends who you ask. Reasonable, maybe, correct, unlikely. It should be noted that thermal shock is a real thing and it applies to both the cold to hot and hot to cold situations. The jury is still out as to what effect this, if any has on airplane engines (in both cases). As noted in the comments to the question there are a lot of trainers out there who have performed countless touch-go's and have had no issues.

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To answer your questions 1) no, a touch and go will not harm the engine, provided it is operated within its established limits and not excessively pushed. 2) It all depends on the flight school in question; some do NOT want students attempting touch and gos, primarily in cases of a short runway the school operates from or just done intentionally to develop better habits in handling the airplane during airport operations. 3) I’m not sure what the guy means by “get the engine properly stabilized” so I can’t say anything about that. Some pilots will like doing touch and gos while others will do stop and gos or taxi backs simply because they don’t like to be rushed with the added workload of a touch and go.

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