Question about the B-17

[grampi]

We have one here by my office selling rides and I noticed something about the plane today. Watching it take off I noticed how slowly it climbed out. I thought that this was very strange considering these planes were designed to carry a lot of weight in bombs and armament...something these planes no longer have...you'd think these things would climb like a banshee considering they fly at a much lighter weight than they did when they were in service. Does anyone know why they they climb so slowly?

[catalinadave]

Re: Question about the B-17

I believe that's to save wear & tear on the engines. I also believe FIFI does the same thing. It's just a way to minimize wear by using a lower power setting.

Dave

[grampi]

Re: Question about the B-17

I've heard it's dangerous NOT to use full power during take-off....is that not true?

[N22252]

Re: Question about the B-17

I've heard it's dangerous NOT to use full power during take-off....is that not true?

Define "Full Power" ...

That said, I will admit that I have been guilty of the extremely dangerous practice of operating a naturally aspirated aircraft engine above sea level on a warm day

[grampi]

Re: Question about the B-17

Define "Full Power" ...

That said, I will admit that I have been guilty of the extremely dangerous practice of operating a naturally aspirated aircraft engine above sea level on a warm day

Being an ex-pilot myself, I recall taking off in my Dad's Cessna 140...it required pushing the throttle control to the stop for take-off...so I naturally assume that all aircraft use full power for take-off...I've also been told take-off is the most critical time for an aircraft (due to having no altitude and a slow speed just above stall) and this is why full power is required...so I've been told....

[AAFO_WSagar]

Re: Question about the B-17

Being an ex-pilot myself, I recall taking off in my Dad's Cessna 140...it required pushing the throttle control to the stop for take-off...so I naturally assume that all aircraft use full power for take-off...I've also been told take-off is the most critical time for an aircraft (due to having no altitude and a slow speed just above stall) and this is why full power is required...so I've been told....

Grampi, I'm not now nor have ever been a pilot, short of a few unofficial lessons... I have been a "student" of flying, however, for most of my adult life.

I'm pretty sure that most/all modern airliners have calculations which dictate power settings versus load/runway length, etc. I don't think they just kick the tires, light the fires and push the throttles to the stops. I suspect, what the -17 crews are doing is right in there with this process.

That said, one of the reasons take off is "dangerous" would be that you are operating at the upper limit of an airplane engine, using less than full available power, on an airplane with surplus power (not all have this, as you know) would be prudent and save engine wear.

[51fixer]

Re: Question about the B-17

Being an ex-pilot myself, I recall taking off in my Dad's Cessna 140...it required pushing the throttle control to the stop for take-off...so I naturally assume that all aircraft use full power for take-off...I've also been told take-off is the most critical time for an aircraft (due to having no altitude and a slow speed just above stall) and this is why full power is required...so I've been told....

If an A/C has really manly power avail and is flown at a very reduced weight you have options a small A/C that lacks Supercharged engines and has a weight to power ratio that is tailored to just being able to lift 2 adults safely.
At full weight with a combat load of bombs, full crew, full fuel and full ammo and armor plate you need full power and a long runway and a few prayers.
Today they are flying at many thousands of pounds under the combat weight. That means you can safely climb at a reduced power setting of the engines and have better performance than they did during the war. The lower power settings decrease strain on the engines and they will last longer, at least hopefully. So the costs of operating decrease, less fuel used, less maint required and they still have a great measure of safety built in.

[supercub]

Re: Question about the B-17

If you had ever seen one loaded....climb, then you'd probably think the typcial climb nowadays isn't to bad. Remember they're probably using less then full power for a couple of reasons.....one, only 100LL is available, and two, less power, less fuel burn. I flew out of Stockton Airport in the 70's and remember seeing B-17's that were air tankers takeoff...........I don't think they got much more the a couple hundred feet per minute climb out of them........of course the temp/density altitude was effecting them too. If I remember right, any of the 4 engine piston tankers in use back then didn't have great climb performance. Certainly was fun watching thme.
Brian

[Plane Nuts]

Re: Question about the B-17

I suggest you buy a ride on the B-17. You will find the acelleration on take-off quite impressive for less than full power. I was.

[goldfinger]

Re: Question about the B-17

They are using reduced manifold pressure for all the reasons noted. Also, the turbos on most of the aircraft are disconnected, and they are also running on 100LL rather than the 130 octane available in wartime.

Chris G.

[Harley909]

Re: Question about the B-17

Not sure which B-17 you saw but we use 40" manifold pressure for takeoff, 35" for METO and climb. Depending on the conditions of the day 130mph indicated will get you around 500-800fpm. Its no rocket but it does the job.

Jim

[grampi]

Re: Question about the B-17

Thanks for all the replies...makes sense...

[AirDOGGe]

Re: Question about the B-17

We have one here by my office selling rides and I noticed something about the plane today. Watching it take off I noticed how slowly it climbed out. I thought that this was very strange considering these planes were designed to carry a lot of weight in bombs and armament...something these planes no longer have...you'd think these things would climb like a banshee considering they fly at a much lighter weight than they did when they were in service. Does anyone know why they they climb so slowly?

According to specs, EMPTY weight is 36,135 lb, while MAXIMUM takeoff weight is a whopping 65,500 lb (29,700 kg).

That's a 29,000 lb difference. Since specs also say they only carried 4,500 lbs of bombs on long-distance missions, you can deduce that most of the weight a B-17 carries is in passengers, fuel and protective armor/defensive weapons, not explosive payloads. Most restored Fortresses are having non-firing weapons re-installed for historic reasons, so their weight still applies.




.

[C_roundy]

Re: Question about the B-17

I truly wonder how heavy they were, at absolute maximum, when they lofted our boys when it really mattered...

[AAFO_WSagar]

Re: Question about the B-17

I truly wonder how heavy they were, at absolute maximum, when they lofted our boys when it really mattered...

I've read a "couple" books written by pilots and crew of the -17, the boys in back had a nasty habit of bringing on more ammo than their plans called for... I'd bet that they were always at or above allowed gross on take off.. If you look at some of the old war videos, their take off was verry slow... some lost an engine, or had other problems and didn't make it very far.

These were some brave cats!