The throttle - please squeeze!

[Pilot DAR]

A flight training organization has returned to the skies over my home - which is a good thing! And, I can hear and witness some of the training in the DA-40. Again, I hear powering up after a low power maneuver - by jamming the throttle to fully open. I cringe! There is no need to jam the throttle open for a planned maneuver, and a few reasons to not do this. Bad that the student is doing this, much worse that an instructor has allowed this to be normal behaviour. I'm not at all a gun person, but the one thing I do remember from instruction was to squeeze the trigger, rather than to jerk it. So, 'same thing for throttle controls!

If you need a reason to adopt this more gentle approach to engine handling, consider the hot thin engine oil after the long climb to get up to do airwork. You close the throttle, and the oil pressure goes down somewhat, more for worn engines. With low oil pressure, and hot oil, you suddenly open the throttle, and the pistons push very hard to accelerate the engine. The crankshaft bearings are still poorly lubricated with thin, hot oil, at low pressure, and the forces on those lubricated surfaces suddenly get very high - needless wear to those surfaces. When you open the throttle slowly, you give the best chance for the oil pressure to build along with the loads on those surfaces.

And, if engine care is not on your mind, more basically think about how it looks if you've been allowed to fly a privately owned airplane, whose owner thinks about things as I do - will they want to let you fly it again if they hear you doing that with it? Be as gentle as you can manage all aspects of the airplane, just so you can show your professional attitude, and impress graceful handling to your students as well. Everything smooth, one day some one in the back might be paying you to fly [them gently]!

[Jhieminga]

Hear, hear...

Playing devil's advocate, what you are not hearing is the endless stream of expletives that the instructor fires at the student after each of those incidents you describe. And on a related note: do you know what engine type is in those DA-40s? If it's a Thielert or Austro Diesel, you can abuse those throttles all day long as the FADEC will manage a lot of things including the acceleration of the engine. As they have single-lever control, they appear to speed up faster than a regular four-banger as the prop is automatically driven to fine pitch as the engine goes to full power. That does not mean that the student should not be taught to do the right thing, but it takes time to instil good habits, and in the process you may encounter a throttle slam or two.

[Uplinker]

Are new students told not to slam the throttle, (or any aircraft control), on their first few lessons ? I cannot remember if I was told that all those years ago, (but I am always gentle with machinery anyway).

Even some airline pilots openly talk about fire-walling the thrust levers, (it's slightly different with gas turbines and FADECS, I know), and some airline pilots couldn't react to TCAS Resolution Advisories gently but put stupid big control movements in.

[cavuman1]

My father, with a degree in Mechanical Engineering from Georgia Institute of Technology (Ramblin' Wreck!) and a degree in Marine Architecture from the U.S. Naval Academy at Annapolis, treated all machinery, especially automobiles, as if they were living entities. He believed that "being gentle", as described above by Uplinker, would yield better performing and longer-lasting equipment. Dad was loaded with common sense!

- Ed

[Hot 'n' High]

Originally Posted by Uplinker

Are new students told not to slam the throttle, (or any aircraft control), on their first few lessons ? I cannot remember if I was told that all those years ago, (but I am always gentle with machinery anyway). ........

Certainly I recall being told that when I was learning (early 90's) ...... and I then drummed it into my Studes once I became an instructor a decade later. All part of Effects of Controls - smooth operation of any control being the aim.

With the throttle, on the old engines, there was the added potential entertainment value of a "rich cut" which would have been very embarrassing when starting to go-around after a PFL into some farmer's field or even on a standard go-around! So it would be briefed again there for those those exercises and jumped on at any point on ANY flight. Nothing changed when I started instructing on the DA-40D TDi despite FADEC supposedly looking after things - still a gentle acceleration/deceleration.

And, like cavuman1's Dad, I fully supported his concept that "being gentle" with technology was the way forward - that view was derived from my initial Aircraft Engineering background from the late 70's onward. Not sure I was ever "loaded with common sense" like his Dad tho! Mrs H 'n' H certainly would like to take issue with any such claim on my part!!!

[Uplinker]

Amen.

Originally Posted by cavuman1

My father, with a degree in Mechanical Engineering from Georgia Institute of Technology (Ramblin' Wreck!) and a degree in Marine Architecture from the U.S. Naval Academy at Annapolis, treated all machinery, especially automobiles, as if they were living entities. He believed that "being gentle"...........would yield better performing and longer-lasting equipment. Dad was loaded with common sense!

- Ed

Absolutely. When you think about machinery - especially an engine - and all the internal forces and stresses it is withstanding hundreds of times a second; the more you can avoid adding to those stresses, the better !

Those of us who have stripped old car engines down and sometimes found bad news and failures, understand that even more !

[Hot 'n' High]

Originally Posted by Uplinker

Amen. Absolutely. When you think about machinery - especially an engine - and all the internal forces and stresses it is withstanding hundreds of times a second; the more you can avoid adding to those stresses, the better !...........

......... and, I forgot to mention in my last post, a key point - well, in my view at least.

By bringing the power up slowly it has 2 added benefits even with FADEC. If you simply bang the power lever up and rely on the FADEC to "sort it" you've sort of entered a "deal" with the FADEC and engine - "I'm at full power ...... now you catch up!". Of course, that's fine if it all works as it should but..........

By bringing the power up slowly, firstly, you give yourself time to listen to, and even watch the instruments (if appropriate and you can), to check the engine is responding as you expect it to (ie is the power coming in smoothly as expected and in sync with my demand or, wait, what on earth is that odd noise????????.........) which leads, secondly, to the fact you can immediately start to bring the power back again from the point you first notice that something doesn't seem quite right.

As an Engineer my 1st Golden Rule has always been - "Never trust technology!". Works quite well that one!!!!!!

[Pilot DAR]

do you know what engine type is in those DA-40s? If it's a Thielert or Austro Diesel, you can abuse those throttles all day long as the FADEC will manage a lot of things including the acceleration of the engine.

Yes, this was a Lycoming powered DA-40 (I know the plane), so it was direct abuse. With the RED A-03 powered DHC-s Beaver I was test flying, jamming the power lever was one test element. Having more power than the P&W being replaced, I was not sure how the plane would handle the additional torque (which is also backwards). I sat on the grass, all set, both hands on the control wheel, and had a pilot friend I trust jam the power lever all the way up (knowing that I might tell him to urgently pull it off again), but it was fine, and the FADEC did limit engine acceleration. That said, I was witnessing fuel supply cut testing at the RED factory in May. We were testing (the previously untested) situation of the low pressure fuel is cut to one bank of the engine. The engine continued to run on the other bank during this test as per my test plan. When the fuel was returned to the deprived bank of the engine, it accelerated 500 RPM to max RPM (governed by FADEC) in 0.2 seconds - so brutally fast! We only did that test three times, for fear of damaging the dynomometer drive. The engine was okay with it, and MT propeller confirmed that if the engine had done it with a prop, the prop would survive. But, my RED A-03 power lever jamming is done!

on the old engines, there was the added potential entertainment value of a "rich cut" which would have been very embarrassing when starting to go-around after a PFL into some farmer's field or even on a standard go-around!

Yup! I was lent a Piper J2 on straight skis to do circuits on the frozen lake. I was warned to be easy on the throttle going around. I was not easy enough, so land back on the ice, and hand prop it out in the middle of the lake - outside the plane, by myself, standing on ice, with no way to secure the plane. I'm sure that the guys watching me from shore were very amused watching me learn a lesson!

When I was new right seat in the Cheyenne, my Captain admonished me a few times that the people in the back were paying a lot for the ride, make it smooth for them. After that, I aspired to fly silky smooth at all times.....

[longer ron]

A slightly light hearted reply to this thread
Just before I left the RAF I arranged a flight in a Bulldog from Abingdon (I was ground crew there with ULAS).
Because the pilot knew I had done a fair bit of flying he very kindly let me do the whole thing from engine start to landing - as we climbed out from take off the pilot was laughing and saying ''I can tell you are an engineer just because of the gentle throttle movement''
One of my earlier trips at Abingdon was in a 10 ship formation of Bulldogs (Capital Formation) - there was much coarse throttle jockeying going on which you wouldn't have liked Mr DAR

[RichardJones]

I believe in treating an aircraft, with respect. Abuse it, then it may turn on you or someone else and bite.
Machinery, has a very long memory. Treat airborne machinery with respect. There are plenty of chances for mechanical failure, so don't try and hasten the process.

[Uplinker]

Frankly, it amazes me that piston engines work at all without exploding, or "letting go", even though I have rebuilt several engines and understand exactly how they work.

F1 Grand Prix engines for example rev to incredible amounts and each piston costs £50,000 !!

Gas turbine engines are more "sensible" with smooth balanced rotating shafts, rather than the mind bending backwards and forwards stop-start of the pistons, con-rods and valves in a reciprocating engine.

[Hot 'n' High]

Originally Posted by Uplinker

Frankly, it amazes me that piston engines work at all without exploding, or "letting go", even though I have rebuilt several engines and understand exactly how they work. ........

............................... and then, in our infinite wisdom, we invented the helicopter!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Jhieminga]

Originally Posted by Uplinker

Gas turbine engines are more "sensible" with smooth balanced rotating shafts, rather than the mind bending backwards and forwards stop-start of the pistons, con-rods and valves in a reciprocating engine.

I guess Sir Frank Whittle was on to something then....

Thanks Pilot DAR for confirming that it's a Lycoming-powered version. No excuse then!

[Manwell]

While I also like to apply smoothness as a principle, rapid use of controls is necessary sometimes, but that's usually of the flight controls to prevent an undesired attitude change, especially at low speed in gusty crosswinds. It took me a while to become assertive enough on flight controls to be able to command an aircraft properly during landing, stalls, spins, and aerobatics. Especially taildraggers.

Rapid throttle use with an aircooled engine could result in a power loss if the carby doesn't have a throttle pump, as the air fuel ratio becomes too lean for combustion, however, the idea that the bearings would suffer increased wear as a result doesn't seem right to me. I used to warm up my car's engine before driving, thinking it was beneficial, before I was told that a BMW tech told my boss that full throttle could be used after start once oil pressure was available. That made me suspect much of what we think is best for engines is based on our emotions, but engines don't care about what we may think, they're mechanical machines subject to physics, not feelings.

[Pilot DAR]

I was told that a BMW tech told my boss that full throttle could be used after start once oil pressure was available.

I read things like that and remind myself that the tech person probably did not own the engine that they were talking about. In any case, my VW diesel goes 18000 km without needing to add any oil. A Lycoming or continental will usually need a liter of oil after ten or twenty operating hours - rather different engine oil systems, internal clearances, and oil pumps. I worked in an aircraft engine overhaul shop for ten years, and "saw things". When I disassembled the O-200 I had owned for 15 years at that point, and out the last 1500 of 3500 hours on, I found minor, but measurable wear on the power side of the crankshaft journels - they were no longer round. I had the crank reground, and it was fine with new undersized bearings. Comparing a state of the art, liquid cooled car engine, with a half century old air cooled airplane engine is not an idea comparison.

As for flight controls, yes, when circumstances require, a swift motion to the stop may be necessary. In most cases, a normal landing in my taildragger will involve several motions of the rudder to the stop, to maintain my centerline control. Moving a GA flight control at any speed is not detrimental to the airplane - it might not be so nice for the occupants, and thus I still promote smooth flight control application for passenger comfort, but the airplane doesn't mind. Turbulence, or a gust correction may not have been able to be anticipated, so as to allow "smooth" flight control application.

On the other hand, if you've got yourself to the point where jamming the throttle is required to maintain "control" of the airplane, you were well behind the plane to begin with. An engine can fail at any time (in 8000 hours, I've had four full forced landings due to engine failure - none were expected). When I'm training someone, and I see them jam the throttle, conditions permitting, they sometimes get a practice engine failure after that!

[Uplinker]

Originally Posted by Manwell

........I used to warm up my car's engine before driving, thinking it was beneficial, before I was told that a BMW tech told my boss that full throttle could be used after start once oil pressure was available. That made me suspect much of what we think is best for engines is based on our emotions, but engines don't care about what we may think, they're mechanical machines subject to physics, not feelings.

As Pilot DAR says, the BMW tech was not the one paying for the engine rebuilds or replacements !

There is no need to fully warm a modern car engine before driving it, but you should be gentle. So I drive, but I won't use large amounts of throttle while the engine is still warming up. So if I encounter a typical slow driver trundling along at 40mph on 60mph limit road, I will not overtake them if my engine is not fully warmed up.

Gunning a cold engine can increase wear, which while not immediately apparent will eventually reveal itself as reduced longevity:

I vividly remember seeing two aircraft ramp guys returning to the staff car-park after their shift one morning. They each got in their cars, and the millisecond their engines started, they roared away at full throttle. It was absolutely no surprise to me that both their engines sounded like buckets of bolts being shaken around !!

Bear in mind that oil pressure indicated on the gauge does not mean that filtered fresh oil has arrived at working pressure in all parts of the engine.

Years ago; before starting a Rover V8 engine that I had extensively rebuilt, I had a tool made so I could prime the engine with oil using my electric drill before starting it for the first time*. I started pumping with the drill and waited to see how long it would take before I saw oil arrive at the top of the engine (with the rocker covers off). It took 20+ seconds before I saw oil. Of course the oil passages had been completely empty, but even so, that was quite a long time before pressurised oil arrived at the valve gear.

So, NO !, I would never use large throttle demands on a cold engine ! Treat it with kid gloves until you notice that the engine cooling thermostat has opened. (You can observe this on the water temperature gauge).

And aircraft engines are always fully and carefully warmed-up before demanding take-off power - with very good reason



*I had of course used special assembly lube on all the bearings and camshaft, which protects an engine during its first start, but I wanted belt and braces.
.

[TowerDog]

Years ago; before starting a Rover V8 engine that I had extensively rebuilt, I had a tool made so I could prime the engine with oil using my electric drill before starting it for the first time

Back in the early 90s I bought a car I had planned to keep a long time so I installed an electric oil pump to build up pressure before start.
and the pump ran after shutdown, probably to protect a spinning turbo from a no-oil scenario.
Great product but the pump could be heard and I got numerous questions and weird looks before starting and after shutdown.
(1992 Pontiac Firebird convertible with a 305 ci V-8, rare bird, not many were made with the rag top)

Back to airplanes: Agree with OP and previous posters, be gentle, live and let live.

[Uplinker]

Nice !

Personally, the sound of a pump running before engine start - especially a nice big V8 - would have improved the 'experience', but then, I am an engineer !

I want to do a similar thing on Mrs Uplinker's car, which has a turbocharger.

[TowerDog]

I want to do a similar thing on Mrs Uplinker's car, which has a turbocharger.

Modern cars with modern lubricants and uh, a gentle throttle foot, may not need such an addition, especially since it may
void warranty and any failure of the added bits and pieces could lead to a lack of ALL oil pressure while happily motoring
down the freeway with not a problem in sight.
(‘This could also lead to an unhappy Mrs and as we know, an unhappy wife is not a good thing, no Sir..)

I have a twin turbo German automobile these days and trying hard to keep my fingers away from the engine compartment
as very little tinkering seems to be required, in fact none: The German engineers followed by fine synthetic oil appears to be a good
combination.

(Apologies for the thread creep, back to a gentle throttle hand for longevity of both man and machine)

[fitliker]

Smooth operator

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