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Take off - which gauge and in what order?

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Take off - which gauge and in what order?

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Old 12th Aug 2018, 02:33
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Take off - which gauge and in what order?

Hey there!

I recently had a discussion with FAA instructor about the take-off procedures, more specifically - the phrase "Engine instruments in the Green"
What we discussed is that this is not a standard practice in some European clubs, mostly former Eastern European schools.
In EU there are a lot of Evektors, Tecnams and similar LSA used for training. As well as some old stuff, like Zlin 42/142/242 /even some 526s/.
The LSAs take off in a matter of 4.5-6 seconds. There is barely time to maintain the course, then you should monitor the speed and when exactly can you check the engine instruments?
OK, RPM is easy, but especially with Tecnam 2002JF - some of those have several gauges which are not clearly visible on a bumpy airfield in take-off mode. Plus the lack of time mentioned.
Then on the Zlins -
many soft field centers out there - which draws your attention outside. Not to mention Zlin 526, where you don't see in front of you the first three seconds.
So my question is:
What is your experience tells you?

P.S. I spoke with an instructor /on Evektor/, who told me he never checked the engine instruments during take-off roll simply because practice showed a lack of time. Even on concrete runway.
Now I understand how this happens in Cessna 152/172, since they are sluggish. But empty 526 for a solo flight can jump pretty quickly, especially on bumpy soft field. Let alone LSAs.
How do you cope with that?
Thanx in advance!
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Old 12th Aug 2018, 12:43
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Like you already said, a number of factors influence this:
1. Time available during the T/O roll in the first place, and the need to look outside
2. Visibility of gauges - some are more in your face than others
3. Type of engine and the gauges that are available (Water-cooled? Constant-speed prop? FADEC?)
4. Historic known problems with the engine and the way this can be detected

I guess IF you have the time, the priority order of checking gauges during the T/O roll would be as follows:
1. Airspeed alive: You can't normally check this during taxi, and you really want to know if the instrument works (no pitot cover, no bugs nesting in the pitot tube).
2. RPM (and possibly MAP) correct for full power. You will want to know the engine is producing take-off power. If you have a fuel flow meter, fuel flow should be correct for full power as well.
3. FADEC warning light. If you have a FADEC, a warning light coming on would be grounds for an immediate aborted take-off.
4. Oil pressure in the green. You will want to know the engine is not going to blow up. Both a too low and a too high indication can be indicative of a problem.

Way down on the priority list:
- Oil, coolant and cylinder head temperature. These will not noticeably change within a few seconds so if they were good before the T/O roll, it doesn't make sense to check them during the roll. They're more for long-term monitoring. Maybe your after take-off checks at 1000' or so are a good place for a peek.
- Vacuum gauge. This has been checked on the runup.
- Volts & Amps correct. Again, this can to a large extent be checked on the runup.
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Old 12th Aug 2018, 12:57
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Do not believe too much in gauges, or in looking at them. Fly the plane by looking at the horizon, listening to the engine, and most of all by the feeling in the seat of your pants. If the engine goes seriously wrong, then you should be able to hear it, and feel it in the performance. If the engine goes wrong in a less serious way, time enough to handle that later. Myself never look at engine instruments before crosswind, and often only on downwind. Know your priorities, first things must come first.

During the take-off run I will quickly glimpse the ASI, to be sure it is more or less alive. There's quite a few reasons it can go wrong, insects or dirt in the pitot tube as already mentioned, but failing to remove the cover seems to occur too.
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Old 12th Aug 2018, 13:29
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I learned the importance of checking ASI before getting airborne one day when we realised it was showing zero on climbout in a microlight.
It was a venturi type rather than pitot/static and after landing we looked in and found a spiders web blocking it.
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Old 12th Aug 2018, 14:39
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Originally Posted by Jan Olieslagers View Post
Know your priorities, first things must come first.

During the take-off run I will quickly glimpse the ASI, to be sure it is more or less alive. There's quite a few reasons it can go wrong, insects or dirt in the pitot tube as already mentioned, but failing to remove the cover seems to occur too.
I absolutely agree. However, apparently, instructors do not teach the young pilots that way anymore.
I do believe that quick glimpse at OIL pressure will be healthy choice, as well as check for established RPM. But on a bumpy field it is almost impossible, let alone in something like Tecnam/Pipistrel/Evektor.
I remember that most of the Eastern Block planes had what is so called Three-Pointer Gauge: Oil Pressure, Fuel Pressure and Oil Tempterature. Latter one was the biggest scale of the three. During take off roll, the fuel pressure needle jumps as much as the aircraft does. Not always and not on every aircraft, but most of those weren't that reliable when its bumpy.
Then the Oil temp was the biggest scale, which beats me. If you have OIL pressure, maybe this should be the most important. Then there was Cyl Head temp, which was quite reliable.
Never payed much attention to those honestly.
Now on the other hand, I saw /more than couple of times/ a student pilot to take off in a 172 with engine instruments still in the yellow after the first start, and still call out "Instruments in the green". Which leads me to the conclusion that this is done mechanically, not thought through.
By the way on Zlins, the run-ups for the engine were done only on the first fly of the day, if you fly half the day or even all day long. When we changed seats, next guy just fires the engine up, check the gauges and go. Sometime even with in-between breaks of more than 45 mins. Never saw that in a Cessna. Which leads me to the conclusion that overall, the flying especially in regards to the engine check was done more recklessly. But that's another subject anyhow.
Even with that, knowing the procedure there is a time-challenge to check everything on take off I believe. I watched a youtube video of Zlin 50 take off. Good luck with checking the gauges on takeoff roll with that thing!
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Old 12th Aug 2018, 14:47
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The first one to look at is the Hobbs/Datcon/Tacho/Breitling reading, whichever one is used for charging for use of the aircraft...
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Old 12th Aug 2018, 15:42
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One more way of doing it is: line up, step on the brakes, set takeoff power, check engine instruments (including RPM), release the brakes, watch the airspeed increase. During the takeoff run on a short runway, the criterion of adequate engine performance is reaching 70% takeoff speed by 50% runway length.
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Old 12th Aug 2018, 15:47
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Originally Posted by Ultranomad View Post
One more way of doing it is: line up, step on the brakes, set takeoff power, check engine instruments (including RPM), release the brakes, watch the airspeed increase. During the takeoff run on a short runway, the criterion of adequate engine performance is reaching 70% takeoff speed by 50% runway length.
Absolutely, but there is another thing to that.
While in training, few instructors will let you alter the procedure.
More important side of things is with tail wheel aircraft. Zlin 526, when set on take off power is with stick 2/3rds forward. If you do that with full power on the brakes it can lead to...well, you know.
Even if you keep the stick backwards with releasing the brakes on full power, the momentum will be greater and you have to be very careful with the stick on take off, because the tail will lift very quickly. Thus, another side of the problem.
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Old 12th Aug 2018, 15:59
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Originally Posted by Sporty123 View Post
Now on the other hand, I saw /more than couple of times/ a student pilot to take off in a 172 with engine instruments still in the yellow after the first start, and still call out "Instruments in the green". Which leads me to the conclusion that this is done mechanically, not thought through.
Depending on the engine (and who you speak to about the engine) it may be perfectly acceptable and safe to take off with the oil temperature still in the "low temperature" yellow band. You can call out "instruments in the green, except oil which is in the yellow" but by the time you finished that callout you are either airborne or have veered off the runway. So if you have noticed and briefed this properly, I'm OK with "instruments in the green", even if the oil temperature is still in the yellow. Nevertheless something like "T&Ps OK" would be better and quicker.
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Old 12th Aug 2018, 17:15
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Oil temp is checked during the run-up, shouldn't be an issue during take-off. I agree it may very between engines, though. On my Rotax 912, 50 degrees (C!) is a requirement even before starting to taxi - though I am not sure this is universally respected.
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Old 12th Aug 2018, 17:24
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Originally Posted by Jan Olieslagers View Post
Oil temp is checked during the run-up, shouldn't be an issue during take-off. I agree it may very between engines, though. On my Rotax 912, 50 degrees (C!) is a requirement even before starting to taxi - though I am not sure this is universally respected.
The presumption to check it during take off roll is that on takeoff power if there is a small leak, you can loose oil, thus see increasing of the temperature. Of course, in case your oil pressure is not reliable. Not that I see a point in that.
Then again, I assume you have something that takes off quickly, having 912 on it.
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Old 12th Aug 2018, 17:37
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Yes - 100-140 metres, depending on weather. Only slightly more with two on board but that occurs rarely.
And BTW even the slightest oil leak will show as a stain on the hangar floor. If no oil has leaked there in days upon days, none is going to leak in an hour or so after rolling out - unless something breaks. And a small leak is not an issue, anyway, as long as one checks the oil pressure from time to time.
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Old 12th Aug 2018, 18:11
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A working airspeed indicator is not required for safe flight. I had all of my students to do a takeoff, circuit, and landing with the airspeed indicator covered so that they would not freak out if they ever lost the ASI.

A working engine is required for safe flight. For an aircraft with a fixed pitch prop the most important gauge to look at is the RPM gauge, for constant speed props it is the MP gauge. After that if time permits a quick in the green scan for the T&P's is nice but not absolutely necessary.

With respect to the power check there are 2 elements that seem to be poorly understood.

The first is the concept of static RPM for fixed pitched props. When the throttle is advanced at the beginning of the takeoff the maximum possible RPM will be well below the redline. For example the acceptable range of static RPM for a C172 N is 2280 to 2400. Any observed RPM outside of this range should be cause for immediate rejection of the takeoff. The part of this check is that you can do it right at the beginning of the takeoff so even in a taildragger you can spare the 1/2 second to check the RPM because you will still be moving slowly with the tailwheel on the ground. I have twice rejected a takeoff because the aircraft would not make the minimum static RPM number and both times major engine issues were identified by maintenance personnel.

The second is for constant speed props. Before you start the engine you should note what the MP gauge is showing. This is called "field barometric" and when full throttle is applied you should see field baro minus about 1/2 to 3/4 inch of MP due to induction system loses. On a average day on a low altitude airport you will see a field baro of about 29 inches but if you are hot and high the field baro will be a lot less, therefore if you don't check what it is prior to start you will have no basis of comparison for the takeoff and thus no way to know if you are getting full power.

Finally if you have the luxury of always flying the same airplane then get used to looking at the engine instrument need position. For example on my Nanchang the engine T & P tri-guage needles form an inverted Y if they are in the normal position. A 1/4 second look will confirm the needle orientation with out my brain having to process any numbers as normal/abnormal.
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Old 12th Aug 2018, 18:47
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At the early stages of training there seem to be a lot of things to do during take off run but as you become more competent you will find that there will be plenty of time during take off to check your instruments and keep it straight, level and increasing in speed. Count the seconds between throttle up and leaving the ground and you will realise that if you keep your cool, you have time to spare.
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Old 12th Aug 2018, 19:03
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Originally Posted by Big Pistons Forever View Post
A working airspeed indicator is not required for safe flight. I had all of my students to do a takeoff, circuit, and landing with the airspeed indicator covered so that they would not freak out if they ever lost the ASI.


With respect to the power check there are 2 elements that seem to be poorly understood.

The first is the concept of static RPM for fixed pitched props.

The second is for constant speed props. Before you start the engine you should note what the MP gauge is showing.
Flight with covered ASI is embedded in many training programs as a simple simulated in-flight failure with which you have to cope. That is not normal flight, especially for more complex aircraft. Z-37 without ASI for example? I wish you best of luck with that. The sole place that the properly working engine will take you with that thing is the place of the crash. Maybe not if you have couple of hundred hours on the thing, but still.

As for RPM vs manifold pressure. Let me give an example. Z-526F and Z-42M. Both aircraft with M137 engine. First one doesn't have manifold pressure gauge, the second one does. Both with constant speed props. Although both are identical prop- and engine-wise, they require different approach, at lest according to the manual. Actually, in my experience I found the manifold pressure is useless gauge on -42M. All the pilots that I know off who flew it think the same. All of them came from Z-526/726, both lacking the gauge.
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Old 12th Aug 2018, 20:01
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Originally Posted by Sporty123 View Post
That is not normal flight, especially for more complex aircraft. Z-37 without ASI for example? I wish you best of luck with that. The sole place that the properly working engine will take you with that thing is the place of the crash. Maybe not if you have couple of hundred hours on the thing, but still.
.
Personally I have not met a non transport category airplane where you can't set a slight nose up attitude early in the takeoff run and then have the airplane fly off when it is ready. As for landing set the appropriate pitch attitude and power setting and you will get the desired approach speed then power to idle and flare. You seem to be saying that with respect to the Z-37 a loss of ASI in flight will " take you to the place of the crash" . If that is the case I would respectfully suggest that anybody who believes that they can't survive a loss of ASI in this airplane should reconsider whether they should be flying it.......

As for RPM vs manifold pressure. Let me give an example. Z-526F and Z-42M. Both aircraft with M137 engine. First one doesn't have manifold pressure gauge, the second one does. Both with constant speed props. Although both are identical prop- and engine-wise, they require different approach, at lest according to the manual. Actually, in my experience I found the manifold pressure is useless gauge on -42M. All the pilots that I know off who flew it think the same. All of them came from Z-526/726, both lacking the gauge.
So how do you set power in these aircraft ?

Last edited by Big Pistons Forever; 12th Aug 2018 at 20:14.
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Old 12th Aug 2018, 20:05
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I'll satisfy myself that full engine power is being developed (which may be by ear only, for fixed pitch aircraft I'm comfortable in). For tricycle singles, I'll keep the nose a little light, and let it fly itself off, I don't refer to airspeed for a takeoff decision. Not too much different for taildraggers, let it get into a nice attitude, and fly itself off. It gets a bit more complex for twins, but then there's more time and procedure to consider airspeed. Eyes out is more important, and if you're feeling and sensing the plane correctly, looking at instruments during the takeoff roll is low priority. If I feel the need to look at instruments during takeoff, perhaps something is not right, and I should abort anyway.
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Old 12th Aug 2018, 21:10
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Originally Posted by Sporty123 View Post
Now on the other hand, I saw /more than couple of times/ a student pilot to take off in a 172 with engine instruments still in the yellow after the first start, and still call out "Instruments in the green". Which leads me to the conclusion that this is done mechanically, not thought through.
I once noticed in the climb out that the oil pressure gauge in a 172 was well above the green - the instructor and I agreed that neither of us had noticed exactly had when it got there (ie neither of us claimed to have been watching it properly on the take-off run). He took control, flew a circuit and landed, and that was that for that day.
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Old 12th Aug 2018, 21:39
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Originally Posted by Big Pistons Forever View Post
So how do you set power in these aircraft ?
Many Zlins are fitted with an Avia airspeed sensitive prop, which automatically maintains constant RPM regardless of airspeed, without a cockpit propeller control.. I haven't flown one and may be incorrect in some detail but if I understand correctly, throttle movement results in an RPM change so you can set power by RPM only. The value of a MP gauge with this prop would not be directly comparable to its value with conventional CS props, where the propeller RPM remains constant with varying throttle opening.

Avia V503 Description

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Old 12th Aug 2018, 21:45
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Just treat every takeoff like a short field, power against brakes quick check and go.
Listen for any unusual noise.
Recent take off in PA28, on the takeoff run began to sound like puffing billy.
At first thought it was just noise coming from my students chepo headset mike.
I looked across, he was wearing a Dave Clark, so thought it ain't that.
We took off and the noise got louder and speed and pitch attitude didn't match as normal.
Vibration increased and I took control at 150' and landed on an alternate runway.
Yep it was a cracked cylinder.
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