Turbocharged engine takeoff ground roll checks - tips?

[hazek]

I’m trying to tighten up my ground roll procedure in my Bravo and would appreciate your insights. When it comes to takeoff, how do you approach scanning the engine instruments? Specifically, I'm focused on:

• making sure the engine is operating properly via the engine instruments and JPI 701
• keeping an eye on any annunciator warning lights as well as the boost pump coming on
• staying on top of MP/RPM redlines

I’m wondering if you have any techniques or tips for maintaining the proper instrument scan and handling any redline issues during the roll. What parameters do you keep a constant watch on, and how do you balance everything in those critical seconds before lift-off? I wind in the power with the vernier throttle on takeoff. And by the time it's open enough so the boost pump light comes on I'm basically at 70kt and rotating. I feel too inside the cockpit. I also have this feeling I would miss a engine instrument redline bust if one would happen to happen.

Thanks in advance for your input.

Edited Tuesday at 08:01 AM by hazek

[larryb]

I look at MP and fuel flow. If you don't have normal fuel flow then you aren't making proper power and/or your temps will soon be too high.

[201Mooniac]

My M20J is non-turbo but I use Power (make sure MP and RPM is as expected), Pressures (check fuel and oil pressures), Airspeed (make sure airspeed is alive), Cylinders (check to make sure all cylinder EGT/CHTs are as expected).  I recently aborted a takeoff because one of my EGTs was way too low, turned out one of my exhaust headers had broken away from the flange.  I've previously aborted a takeoff when at a high elevation airport I miscalculated what I should expect for the MP, turned out it was correct but I'm glad I checked it out on the ground rather than had a problem in the air.

[Z W]

I don't use the vernier throttle to dial in on the takeoff roll - I push the button and slowly but firmly advance to full throttle. The vernier is too slow and it's hard to feel when you're at full throttle.

Confirm turbo operation by verifying manifold pressure - you can also hear and feel it kick in passing 28-30" MP.

Verify power set - MP, RPM, and fuel flow as expected (36" MP, 2700 RPM, 22-23GPH for me, your numbers will vary).

After that, eyes on the airspeed indicator and out the window. You'll be flying too soon to look at much else. Scan for warning lights and to confirm power set as time allows. Be ready if anything is off to pull the throttle and stop on the runway or land straight ahead.

[Fritz1]

For the density controller to work correctly you need about 180 dF oil temp, I turn the boost pump on manually when I enter the runway just in case the throttle switch fails, line up, check cowl flaps open, push mixture rich, if enough runway slowly turn in boost, watch RPM rise to 2575, check oil pressure, check fuel flow 29-30, check boost, minimum 35, maximum 37" as a function of induction air temperature, which is typically between 90 and 150 dF, watch airspeed, rotate between 70 and 75 kt depending on weight, positive rate, no runway remaining gear up, flaps up check boost below 37 with intercooler full flow, 1000 ft reduce power 34" 2400, boost pump off, fuel flow around 23, lean for 1580 TIT, cruise climb about 120KT, keep CHTs below 400 dF. Depending on weight the Bravo will climb at around 600 fpm through 18000 ft, when altitude captured close cowl flaps, let speed build up, reduce boost to 30", reduce rpm to 2300, fuel flow about 18.5 gph, produces about 1580 TIT, 350-380 CHT and about 185 KT TAS in my TKS Bravo, others may be 5KT faster, power is about 78%, reducing power I take out 2" per minute, keep TIT between 1550 and 1580, CHT reduction not more than 15 dF per minute, Lycoming says 50 dF per minute is permississible, descent 750 fpm, don't go below 18" at that descent rate, engine starts driving propeller and rings may start fluttering, with gear down power can go below 18", don't push mixture rich for landing, just fouls plugs, keep mixture where you had it during descent 

[hazek]

Seems like all responses so far deviate from the POH checklist.

On 2/2/2025 at 3:22 AM, Z W said:

The vernier is too slow and it's hard to feel when you're at full throttle.

Can you explain what you mean by that? What exactly is hard to feel winding it in instead of pushing it in? How do you protect yourself against overboosting if you push it in, winding it in gives me more control where I can stop before that.

 

19 hours ago, Fritz1 said:

I turn the boost pump on manually when I enter the runway just in case the throttle switch fails

That's not a bad idea, then I don't need to watch for that coming on.

[Fritz1]

Installing IAT gauge will help you verify what the density controller does, intake plenum is pre-drilled and tapped, take plug out, install probe

[Fritz1]

IAT probe wires to an EDM700 monitor and any other monitor

[Z W]

1 hour ago, hazek said:

Seems like all responses so far deviate from the POH checklist.

Can you explain what you mean by that? What exactly is hard to feel winding it in instead of pushing it in? How do you protect yourself against overboosting if you push it in, winding it in gives me more control where I can stop before that.

It's hard to feel because turning the vernier lets you really crank and put some pressure on the cable against its stop in the engine compartment, which you don't want to do, if you keep turning it in past full throttle. You are not supposed to use the verniers to advance the controls too close to the dash. My POH has warnings not to turn the prop or mixture closer than 1/8" using the vernier, though oddly enough, not the throttle, I just noticed:

 

You can feel it hit the stop if you slowly advance the vernier in, like during cruise, but I find it hard to do while spinning it in relatively quickly and also rolling down the runway for takeoff. I find it easier to feel when you have reached full throttle if you just push the button and slowly, steadily, but firmly advance the control in. Your experience may vary, this is just what I do.

My TSIO-360-MB engine has an automatic wastegate that under normal circumstances prevents overboosting, so full throttle is proper for takeoff. Under certain temperatures and density altitudes, it may overboost by 1-1.5 inches, which is allowable for a short time, and if it does, I just dial out a little throttle with the vernier. I was under the impression the Bravos also have an automatic wastegate and do not overboost normally, but I have never flown a Bravo.

My takeoff practice is consistent with my POH, shown below. I do use 36" instead of 40" because my engine was changed to a MB series as part of the 262 conversion.

[Fritz1]

The Bravo has an automatic wastegate, mine tended to underboost at high IAT and overboost at low IAT, hence the IAT gauge which allows to fine tune the takeoff boost, i.e. back off manually at low IAT, density controller is now set to produce about 37" at 150 dF IAT which is needed for a hot and high takeoff

[Marc_B]

2 hours ago, Z W said:

My POH has warnings not to turn the prop or mixture closer than 1/8" using the vernier, though oddly enough, not the throttle,

I thought that was referring to 1/8" from full forward.  i.e. if you use the button to push all the way forward it will stop, but you can still twist in more and it could bind or perhaps could damage the vernier mechanism?  I read that POH statement as you shouldn't twist the vernier more than 1/8" from fully forward.

[hazek]

8 hours ago, Z W said:

It's hard to feel because turning the vernier lets you really crank and put some pressure on the cable against its stop in the engine compartment

Interesting, I think I'm mishandling it yeah. There is a bit of freeplay at full throttle in my plane where if I wind the throttle in after I'm reducing power initially nothing happens. So probably I'm going past that stop that I should not go past of. Btw the Bravo checklist has the same wording as yours but also only for the prop and mixture control. Perhaps the vernier throttle is an option so they didn't put it in by default? Makes no sense it should be treated differently.

And yes, automatic waste gate in the bravo, so I guess overboost should not happen.

8 hours ago, Z W said:

My takeoff practice is consistent with my POH, shown below.

How do you follow item 6? Please explain in as great a detail as possible.

[hazek]

6 hours ago, Marc_B said:

I thought that was referring to 1/8" from full forward.  i.e. if you use the button to push all the way forward it will stop, but you can still twist in more

I didn't realize this.

[hazek]

10 hours ago, Fritz1 said:

IAT probe wires to an EDM700 monitor and any other monitor

So you're saying having the IAT indication and knowing the numbers is how you verify your engine will not overboost?

[Z W]

9 hours ago, Marc_B said:

I thought that was referring to 1/8" from full forward.  i.e. if you use the button to push all the way forward it will stop, but you can still twist in more and it could bind or perhaps could damage the vernier mechanism?  I read that POH statement as you shouldn't twist the vernier more than 1/8" from fully forward.

Yes, I agree, that is what I was trying to say. But if you are trying to spin the throttle in from idle all the way to full forward, while rolling down the runway, it's hard to tell when you're getting past the fully forward position.

[Z W]

3 hours ago, hazek said:

How do you follow item 6? Please explain in as great a detail as possible.

Item 6 - Engine Instruments - Check proper indications.

Verify expected MP, RPM, and fuel flow once you've set full throttle. If your MP is a little high, reduce throttle until it's not. If any of them are unexpectedly low, abort takeoff and figure out why on the ground.

Note - it's not uncommon for RPM to be about 50 below maximum until your airspeed comes up and reduces the load on the prop. Mine goes from 2650 while starting the roll to 2700 around 40-50 KIAS.

With a turbo, you have the benefit of the fact that it should always make full power at any airport, so this is even simpler than a naturally aspirated plane and is the same every time.

[hazek]

1 hour ago, Z W said:

erify expected MP, RPM, and fuel flow

What about any other gauges such as Oil Pressure, Oil Temp, TIT, Fuel pressure, JPI700?

[wombat]

You are all making this WAY WAY WAY too complicated.

 

Slowly advance the throttle over 2-5 seconds and when you get to full throttle, glance down at the engine instruments and see if there is anything different from normal.   And have done some transition training so you know that 'normal' is actually about correct.

If yes, keep going.  If not, abort.

[Andy95W]

9 minutes ago, wombat said:

Slowly advance the throttle over 2-5 seconds and when you get to full throttle, glance down at the engine instruments and see if there is anything different from normal.   And have done some transition training so you know that 'normal' is actually about correct.

If yes, keep going.  If not, abort.

I agree with Wombat, above.

One additional note- the JPI 701 is a good instrument but is small and not easy to read.  Your airplane can be upgraded to a JPI 730, 830, or 930 that are larger and easier to interpret at a glance so that you can monitor the engine more quickly.  Your engine probes would be reused and more can be added to make the engine monitor more useful.  The 930 is a legal replacement for all of your existing engine gauges if you wanted that.

https://www.aircraftspruce.com/catalog/inpages/jpi730830upgrade.php

[Pinecone]

Encore converted 252 here, so TSIO-360-SB.

I am also in the camp of a smooth push, no vernier.  I don't have a vernier on the throttle, but even if I did, I would push the button, and do a smooth push.

I push the throttle to full, then about 1/2 way into the take off, I check the MP.  The limit is 39 inches, but there is a note that up to 41 inches is acceptable for up to 2 minutes.  So I am not worried about a slight over boost.

I also check it after the gear and flaps are up, as it sometimes creeps up. Maybe a bit of ram air.  

I don't recall ever seeing it 40 inches, maybe 39.2 - 39.5 mostly if not slightly below 39, depending on temp.

[hazek]

1 hour ago, wombat said:

You are all making this WAY WAY WAY too complicated.

Well, possibly. But in my few hours of flying my plane I already had a partial engine failure where I potentially missed the warning signs on the takeoff roll taking it in the air when I could have aborted. 
My best idea right now is to step on the brakes, get 2000 RPM or so, observe the JPI701 for proper indications and then release brakes and do what you suggest.

[hazek]

1 hour ago, Andy95W said:

Your airplane can be upgraded to a JPI 730, 830, or 930 that are larger and easier to interpret at a glance so that you can monitor the engine more quickly.

I am aware but I co-own so I'd have to convince my partner. And that's unlikely. But we have space around it for the bigger screen:

[gabez]

On 2/1/2025 at 11:29 AM, hazek said:

I’m trying to tighten up my ground roll procedure in my Bravo and would appreciate your insights. When it comes to takeoff, how do you approach scanning the engine instruments? Specifically, I'm focused on:

• making sure the engine is operating properly via the engine instruments and JPI 701
• keeping an eye on any annunciator warning lights as well as the boost pump coming on
• staying on top of MP/RPM redlines

I’m wondering if you have any techniques or tips for maintaining the proper instrument scan and handling any redline issues during the roll. What parameters do you keep a constant watch on, and how do you balance everything in those critical seconds before lift-off? I wind in the power with the vernier throttle on takeoff. And by the time it's open enough so the boost pump light comes on I'm basically at 70kt and rotating. I feel too inside the cockpit. I also have this feeling I would miss a engine instrument redline bust if one would happen to happen.

Thanks in advance for your input.

MP/FF/RPM and scan for all 6 cylinders firing. as I climb I keep an eye on the FF and RPM. if my FF is at 25 GPH usually my TIT is at 1400 through the climb

[dkkim73]

Acclaim not Bravo, but:

From transition training, I will usually hold brakes and throttle up to 2300rpm, checking the engine gauges on the MFD, primarily looking for any new variance in the EGTs. Glance occasionally on the roll, "gauges are green and airspeed's alive". Otherwise it's mostly about feeling the response esp. the turbos. 

Above discussion makes me resolve to note fuel flow more specifically. Everything's full forward until TOC so I don't usually think too hard about TIT, but that would be a cross-check on fuel flow. 

 

[wombat]

1 hour ago, hazek said:

My best idea right now is to step on the brakes, get 2000 RPM or so, observe the JPI701 for proper indications and then release brakes and do what you suggest.

Since I fly out of a 2700' runway, I also hold the brakes while I increase throttle.  I increase to 29" and do my engine scan.   Then I release the brakes and advance the throttle the rest of the way.