Return from Nagasaki to Okinawa by B-29 “Bockcar”

[Vraciu]

I agree that being "on step" is a myth.  However I've found that your first statement might not be true in all cases.

The B-24 is a quirky airplane.  It "seems" to have a step.  We used 30 inches and 2000 RPM for cruise which gets you about 180 IAS at around 1500 MSL.  If you get a bit ham-fisted with the elevator you can get the airplane slowed up a bit (5-10 mph) and it just doesn't want to get back up to the 180 you had before unless you bring the power up or descend a bit.  You learn to be smooth.

We both agree that's not a step.   That's just normal cruise.   I don't have any data for the airplane but you might just be experiencing the result of a narrow range between front side and back side of the power curve.   Either that or it just takes a long time to accelerate back to 180 because there is so little relative power available for the condition.

Jets will do this, too.  An OAT spike and it falls on its butt.  You can ride it out and slowly accelerate as you burn fuel or descend to a lower altitude.   But cruise speed is cruise speed.   You can dive to it or climb to it--but it always ends up at the same spot when everything stabilizes.

[Vraciu]

What jets have you flown? Still fly? I was checked out in the Cessna 152 and Piper Warrior.

Everything except McDD, Boeing and Canadair (although I have plenty of hours in their jump seats).

Flown a few warbirds here and there, as well.  Nothing special.  A-4, Strikemaster, T-28, PBJ.    Gonna try to get a ride with one of my buds who flies a P-51 for a foundation that tours the country every year. 

Still fly.  Still instruct.   Am in Africa right now flying executive jets for high rollers.   Been a fun adventure so far.   

[BuckShot]

"Nothing special" I wish I could say that!

The a-4 is of one of my favorite hairdryers.

Thanks

[DaveBB]

Also, I'd like to correct the name of this thread.  I've seen "Bock's Car" at Wright Patterson AFB Museum.

[RonB29]

    The name written on the nose of the plane is one word "BOCKSCAR."  In Sweeney's and Tibetts' biographies, but not in Olivi's, the writers/editors changed it to the correct English possessive form "Bock's Car."  I prefer the name written on the airplane.
    The interesting question to me is; does a flight path of repeated diving and leveling out, as Sweeney describes, give better fuel economy that a steady descending flight path at constant  airspeed?  I don't think that it does, but a simulator might prove me wrong.

[Vraciu]

"Nothing special" I wish I could say that!

The a-4 is of one of my favorite hairdryers.

Thanks

Great machine.  The first three times we rolled it I whacked my head against the canopy.  It is eye watering.

 

[save]

The big problem at 30k+ up is the jetstream that either help you where you're going, or it's slowing you down.

[Vraciu]

The big problem at 30k+ up is the jetstream that either help you where you're going, or it's slowing you down.

That's why LeMay went to 5000 feet with firebombs and burned Japan to ashes. 

[earl1937]

That's why LeMay went to 5000 feet with firebombs and burned Japan to ashes.

For what ever it is worth to this discussion, this is how we did it! Call it a step or whatever, but when sitting up cruise, we would normally level off about 500 feet above cruise altitude and accerate as we descended back to assigned altitude. Then, as the fuel burned off, lowering our weight, which moved the C.G. aft a bit, we had to retrim and descend again another 3 to 500 feet to get back on "step". This gave us about 4 to 6 knots increase airspeed and didn't hurt the fuel burn. Once we got down to 15,000, it was pretty much 30 X 2,000 RPM back to home plate!   

[Zimme83]

I have hard to believe that it would increase the range in any significant way. It is just trading altitude for speed. Its a good way to save some fuel if you are at a certain distance from the field were you have to decend anyway but other than that i dont see any benefits from doing it (Unless you can catch better winds at a lower altitude of course).

[RonB29]

For what ever it is worth to this discussion, this is how we did it! Call it a step or whatever, but when sitting up cruise, we would normally level off about 500 feet above cruise altitude and accerate as we descended back to assigned altitude. Then, as the fuel burned off, lowering our weight, which moved the C.G. aft a bit, we had to retrim and descend again another 3 to 500 feet to get back on "step". This gave us about 4 to 6 knots increase airspeed and didn't hurt the fuel burn. Once we got down to 15,000, it was pretty much 30 X 2,000 RPM back to home plate!   

I think you have a very good point.  Maj. Sweeney is just describing re-trimming for the proper descent rate as the weight decreases.  My computer program shows that at 30,000ft and a glide angle of -0.012 rads, the speed should increase by 1.4 mph as the weight decreases from 85,000 to 84,500 lbs. 

[Vraciu]

For what ever it is worth to this discussion, this is how we did it! Call it a step or whatever, but when sitting up cruise, we would normally level off about 500 feet above cruise altitude and accerate as we descended back to assigned altitude. Then, as the fuel burned off, lowering our weight, which moved the C.G. aft a bit, we had to retrim and descend again another 3 to 500 feet to get back on "step". This gave us about 4 to 6 knots increase airspeed and didn't hurt the fuel burn. Once we got down to 15,000, it was pretty much 30 X 2,000 RPM back to home plate!

That's not a step.   

There is no step.

For a given power setting there is only one cruise speed.   You can dive down to it or climb up to it.   You will always stabilize at the exact same cruise speed for a given configuration.

Even B-29 instructors who taught this method testify to the fact that the stabilized cruise speed always wound up the same. 

There is no magic way to gain knots in level flight.

[Vraciu]

I have hard to believe that it would increase the range in any significant way. It is just trading altitude for speed. Its a good way to save some fuel if you are at a certain distance from the field were you have to decend anyway but other than that i dont see any benefits from doing it (Unless you can catch better winds at a lower altitude of course).

Exactly.    And you are losing True Airpseed at a rate of two percent per thousand feet (standard day). 

[Vraciu]

I think you have a very good point.  Maj. Sweeney is just describing re-trimming for the proper descent rate as the weight decreases.  My computer program shows that at 30,000ft and a glide angle of -0.012 rads, the speed should increase by 1.4 mph as the weight decreases from 85,000 to 84,500 lbs.

Which is not a step. 

[RonB29]

Unfortunately, “getting on the step,” seems to have two distinct aspects.  The first is a process or flight path maneuver to get to the best-range cruise condition.  If the plane has only modest extra power for acceleration, it avoids the long time-constant of level-flight acceleration to best cruise speed.  The second aspect is the idea that the cruise state reached by this maneuver, the final “step” airspeed, is extra fast; a hysteresis situation that requires a certain approach path.  Many (most?) pilots don’t believe that the final speed is anything unusual.
   The 1945 Boeing POH recommends climbing 500 ft. above the intended cruise altitude for each 10,000 ft. of cruise altitude.  They call the best-range speed ‘the step.”  It must have been the common term at that time.  They never claim that it is extra fast.
   In Sweeney’s description he is repeating the maneuver process again and again.  So the question is not; is the final speed is extra fast?  But, is the average speed of the maneuver faster?  Is it faster than what?  I think that it should be compared to a flight path with a constant descent rate at the best-range speed.  The descent rate allows the power and fuel flow to be reduced.  As Earl1947 points out, as the weight decreases you must re-trim if you keep the same power, and the speed will increase.  Is this what Sweeney was doing, or was the descent and flare more emphatic?