Engine break-in: leaving gear & speed brakes extended

[hais]

In last engine break-in, this fire-breathing dragon was reaching 180 KIAS to keep the CHTs up. 

We have another break-in coming up, this time in busy controlled airspace. Was wondering: any issues against leaving the landing gear and speed brakes extended to keep the speed in the 130-140 KIAS range? 

[Danb]

Why not, as u know the first hour is the most critical 

[201Steve]

180 kts will get you down the road and out of busy airspace in a hurry. 

[larryb]

What’s wrong with 180 knots?

[PeteMc]

Can you run at the power you need to with the gear extended? 

 

[Ragsf15e]

I doubt it will hurt it but personally I don’t want to intentionally exceed my gear down speed of 120kts.  I think you’re better off just climbing up to 5k or so and letting her eat!

[toto]

3 hours ago, hais said:

In last engine break-in, this fire-breathing dragon was reaching 180 KIAS to keep the CHTs up.

What’s the concern about keeping CHT up? When I have done break in flights, the goal is to run continuously at high power, but you want to keep the CHTs down as much as you can. Lots of airflow and lots of mixture. I don’t think high CHT is your friend. 

[jlunseth]

I am also breaking in my engine. I don't hesitate to keep the speed brakes out to slow the airframe. They are rated for the Vne speed of the aircraft. I would not want to exceed the gear speed though, with the gear deployed. Mine is 132 kts. The leading edges of the gear doors are unsupported sheet metal, I have had pieces of the leading edges of the gear doors, especially the starboard one, sheer off several times, to the point where I don't even try to repair them anymore. Wasn't exceeding gear speed, they are just vulnerable. TCM recommends dialing the RPMs way down in order to keep the cylinders warm. For engine break-in, I routinely dial the RPMs down to 1800 on final in order to be able to keep the power up. Don't know that I would go that low for a sustained cruise though, but maybe look at your POH tables and use the lowest cruise RPM in the tables. Probably 2200. You might try the kitchen sink, i.e. leave the gear deployed, speed brakes out, and full flaps. Obviously, if the airframe starts to exceed the V speed for one of them you would need to slow and take that appendage in, probably the flaps first. But it might keep the airframe from exceeding any of the V speeds to begin with.

I am nearing 50 hours and the engine is probably pretty much broken in at this point.

[jlunseth]

15 hours ago, toto said:

What’s the concern about keeping CHT up? When I have done break in flights, the goal is to run continuously at high power, but you want to keep the CHTs down as much as you can. Lots of airflow and lots of mixture. I don’t think high CHT is your friend. 

TCM wants the CHT to be between 300 and 380 and to limit cold and low power operations. Heat and pressure to prevent deposits and to seat the rings hard against the walls.

[toto]

9 minutes ago, jlunseth said:

TCM want the CHT to be between 300 and 380 and to limit cold and low power operations. Heat and pressure to prevent deposits and to seat the rings hard against the walls.

Yes, you want to avoid low power settings, extended idle and long or steep descents - but if you’re running at or near max power for an hour, my concern would be keeping the cylinders cool, not warm. 

[hais]

11 minutes ago, toto said:

Yes, you want to avoid low power settings, extended idle and long or steep descents - but if you’re running at or near max power for an hour, my concern would be keeping the cylinders cool, not warm. 

I formulated poorly - yes, the intention is to run at high power and stay within recommended temp range. 

[hais]

1 hour ago, PeteMc said:

Can you run at the power you need to with the gear extended? 

 

Yes, gear extended speed is 165.

[hais]

3 hours ago, 201Steve said:

180 kts will get you down the road and out of busy airspace in a hurry. 

After major surgery, you want to stay nearby for the first hour 

[hais]

2 hours ago, larryb said:

What’s wrong with 180 knots?

Lots of trainers around you doing 80 knots, and ATC likely would prefer you stay below 2000 ft, so slower is better. 

[toto]

1 minute ago, hais said:

After major surgery, you want to stay nearby for the first hour 

Definitely. For the first break-in flight, I orbit the airport at 2500 AGL. Low enough to get good power, but high enough to glide to the runway from just about any point in the circuit. 

[Shadrach]

11 hours ago, hais said:

I formulated poorly - yes, the intention is to run at high power and stay within recommended temp range. 

Are you struggling to keep CHTs above 300° at max power?  If not, this is much ado about nothing.

I broke my cylinders in Lean of Peak in the winter time. Never exceeded 340° during break in.  In the low to mid 300° range well inside an hour. We establish excellent oil control well within five hours. 

Heat does not help brake in cylinders, high, consistent, internal cylinder pressure breaks in cylinders. This is why varied RPM is recommended; It varies where peak pressure occurs in the stroke helping to break the bore in evenly.

Continental is simply using recommended CHT range as a proxy for minimum internal cylinder pressure (>300°) and adequate cooling (<380°). No one that I know of has ever had to employ unconventional techniques like speed brakes and extended gear to perform a healthy break in.

[Shadrach]

13 hours ago, Ragsf15e said:

I doubt it will hurt it but personally I don’t want to intentionally exceed my gear down speed of 120kts.  I think you’re better off just climbing up to 5k or so and letting her eat!

120kts?  You wish!!!...and so do I.  Odd that the J with the more fragile lower gear doors gets 132kts extended and 107kts for retraction.  I am sure my arm could handle the extra load.

[Ragsf15e]

27 minutes ago, Shadrach said:

120kts?  You wish!!!...and so do I.  Odd that the J with the more fragile lower gear doors gets 132kts extended and 107kts for retraction.  I am sure my arm could handle the extra load.

Well ok, mine is 120mph, not kts, 

It does seem weird that the gear speeds change throughout the years without changing the airframe.

[Shadrach]

26 minutes ago, Ragsf15e said:

Well ok, mine is 120mph, not kts, 

It does seem weird that the gear speeds change throughout the years without changing the airframe.

It's regulatory/certification inertia. There are many "paper" changes on later models that would likely encompass all models if not for the regulatory challenges. Why is your Vfe 20mias higher than mine?...

 

 

[hais]

14 hours ago, Shadrach said:

Are you struggling to keep CHTs above 300° at max power?  If not, this is much ado about nothing.

I broke my cylinders in Lean of Peak in the winter time. Never exceeded 340° during break in.  In the low to mid 300° range well inside an hour. We establish excellent oil control well within five hours. 

Heat does not help brake in cylinders, high, consistent, internal cylinder pressure breaks in cylinders. This is why varied RPM is recommended; It varies where peak pressure occurs in the stroke helping to break the bore in evenly.

Continental is simply using recommended CHT range as a proxy for minimum internal cylinder pressure (>300°) and adequate cooling (<380°). No one that I know of has ever had to employ unconventional techniques like speed brakes and extended gear to perform a healthy break in.

No, no trouble with temps. The high power setting recommend for break-in accelerates the airplane to speeds that are unsafe in the environment. One option is to go away from the airport - not a great one. Another is to increase drag. 

[Shadrach]

21 hours ago, hais said:

No, no trouble with temps. The high power setting recommend for break-in accelerates the airplane to speeds that are unsafe in the environment. One option is to go away from the airport - not a great one. Another is to increase drag. 

I guess I misunderstood the first sentence of your first post. But yea if your uncomfortable which high power operations at you airport then go elsewhere.  I’m based at a controlled field they are fine with me flying patterns at 3700’AGL. That puts me 2000’ above piston traffic and 1500’ above turbine traffic. The very few traffic conflicts that may occur at that altitude are easily managed with controller input. I have been vectored over many Class B airports over the years and it’s typically done at low altitudes because there is little to no traffic directly over those airports.

[takair]

Last break in I did, I climbed until I was at 75-80% wide open… which put me about 5500. Think I was a little over 75%. Then I did wide oval runs while keeping the airport in the glide circle of Foreflight. Needed to be smooth air since I was near redline. In my bird I could not get anywhere near 75% power below gear speed, but OPs appears much higher.  Ref. The tower, I told them in advance what I was doing and they had no problem with it. I think speedbrakes out might be nice, but I think the gear doors would take a serious beating. 

[Shadrach]

4 hours ago, takair said:

Last break in I did, I climbed until I was at 75-80% wide open… which put me about 5500. Think I was a little over 75%. Then I did wide oval runs while keeping the airport in the glide circle of Foreflight. Needed to be smooth air since I was near redline. In my bird I could not get anywhere near 75% power below gear speed, but OPs appears much higher.  Ref. The tower, I told them in advance what I was doing and they had no problem with it. I think speedbrakes out might be nice, but I think the gear doors would take a serious beating. 

Be interesting to see your POH. The 68 F power tables show 77% available at WOT 2700rpm @10,000

[takair]

6 hours ago, Shadrach said:

Be interesting to see your POH. The 68 F power tables show 77% available at WOT 2700rpm @10,000

You are right….I was using 2500rpm….which puts it at about 82% at 5000.  My POH shows 75% at 2700rpm at 10000….  I just don’t like the way it sounds at 2700 in cruise….