quote:

Originally posted by M1Garandy:
NTSB Preliminary Report is out: https://app.ntsb.gov/pdfgenera...Type=Prelim&IType=MA

Anybody care to translate that? It states the flaps were retracted. I assume a normal landing would require at least SOME flaps - does this indicate pilot error or flap malfunction?

Hmm, report also mentioned a "rough mag(neto)" on No. 4. Are we back to my chain-of-events theory (weak engine and undeployed flaps)?

Flaps in to reduce drag and extend the pattern at a higher speed...Juan Brown has a short video on this.

Still more work to be done. They flew pattern at 300 feet sounds like the could not climb.

quote:

Originally posted by Hound Dog:

quote:

Originally posted by M1Garandy:
NTSB Preliminary Report is out: https://app.ntsb.gov/pdfgenera...Type=Prelim&IType=MA

Anybody care to translate that? It states the flaps were retracted. I assume a normal landing would require at least SOME flaps - does this indicate pilot error or flap malfunction?

B-17 manuals I've seen have 1/3 flaps listed.

Not that a plane can't land NO flap, but the approach and landing speeds would be different, with the no-flap speed typically being faster (at least all the airframes I've flown in).

But with engine issues, they may elect to fly no-flap to keep drag down.

Wow, they struck the approach lights 1000ft short of the runway, then wheels touched down 500ft short of runway. They were way too low on approach. Either they misjudged it or didnt have enough power/stalled. Odd thing about the flaps, but some quick google-fu shows that the simple slit flaps on the B17 were used for drag as well as lift, so maybe having the flaps retracted was correct? Every video Ive found on youtube of B17s landing shows them with flaps down on approach and landing.

The airplane was 500' above ground level when the pilot notified ATC. It entered the downwind at 300'. Clearly it was drifting down, and maintaining altitude was either not an option, or the crew sacrifice altitude. Given that the preliminary report indicates impact markings consistent with a feathered engine on #4, the inference is that the far right engine was shut down. It can't run, feathered. Additionally, it requires a second operation after shutdown to feather the propeller.

The report indicates that damage to the #3 propeller is consistent with being partially feathered. This means that while the enigne may have been shut down, the propeller was turning slowly, but either hadn't completed the feathering process, or was unsuccessful. Again, it takes engine oil to drive the propeller into feather; if left running, the feather pump motor will drive it right back out of feather. Either way, the fact that damage indicates it wasn't producing power at the time of impact indicates that it was producing drag, and likely considerable drag.

Often a hydromatic propeller when feathered will continue to turn, sometimes slowly, sometimes more quickly; any motion imparted by the slipstream has to overcome internal drag in the engine, which is massive, and results in a VERY significant drag rise for the aircraft. An unfeathered propeller will produce considerably more drag than if a plywood disc of the same diameter as the prop arc were put in place of the propeller.

The B-17 is a VERY low-performance airplane to begin with. Shut down one engine, it decreases substantially. Shut down another and level flight can become problematic. If a failure to feather occurs on either one, the aircraft will be drifting down.

With the implication of the preliminary that two engines were unpowered on the right side, full rudder and additional bank angle would be required to maintain directional control. Banking must be shallow, and turns to the left will be limited substantially. In this case, a left bank would be required to maintain heading, in addition to full rudder. This means a loss of lift and further increase in drag. The aircraft flew a right pattern to runway 6, as the report describes a right downwind leg (opposite the direction of landing) at 300' above ground. By comparison, normally on a VFR pattern, an aircraft should be no lower than 500' when turning final, and should be 1000' on the downwind leg.

With two engines out, increasing drag further with flaps would be problematic until short final approach. Bear in mind that lowering of flaps in an open-center hydraulic system, with one. hydraulic pump inoperative is time consuming, and that time may have been needed to get the gear down. Gear first, as it's a priority that low and in the pattern, and even then, gear would need to be left until the last possible moment due to drag rise and drastically reduced performance in an already low-performance airplane.

Absence of flap in many of these older airplanes produces significant changes in stall speed; by comparison, the B-24 can have a 50 knot change in stall speed with flaps vs. no flaps. The importance of this is the need to fly a higher speed without flaps, which means that one is unable to fly a minimum drag speed, which may mean an increased rate of descent. Adding flap, however, increases drag, and reduces climb performance. The aircraft was already below final approach altitude at the outset. This becomes a case of damned-if-you-do, damned-if-you-don't.

Bear in mind also that the B-17 uses split flaps: these use the lower surface of the wing to deflect downward, while maintaining the same camber of the upper surface at the trailing edge: they increase drag more than lift. Flaps increase both lift and drag and at lower flap settings, many flap systems increase lift more than drag. The B-17 split flap system does increase lift slightly, but begins acting as a speed brake by increasing drag the moment that any flap is applied, and increases substantially as the flap deflection is increased.

Collings Foundation tends to use a long supply of volunteer pilots who fly when they can; like the CAF and other groups, they oftne use airline pilots who can jumpseat to the airplane and who will pay their own hotel and travel expenses. The captain on this flight was not an airline pilot, as he lacked an airline transport pilot (ATP) certificate. He had only one type rating, and that for the B-17. The copilot had a number of type ratings and an ATP certificate, indicating that he was an airline pilot (but given his second class medical, likely retired). 14,000 hours for the captain, with no ATP indicates perhaps an ag background or something along those lines (it's unusual to get to 14,000 hours and not obtain an ATP). It's very possible that neither had been exposed to this type of event before.

In open center hydraulic systems, the control (flap, gear, etc) must be placed in the desired position (down, in this case) and held there until the desired setting is achieved, then physically moved back to the neutral state. It requires dedicated attention and not just a control movement, as the control can go too far, or flaps, gear, etc, could retract if moved too far in the opposite direction.

It's quite possible with both engines out on one side and the gear out, turning to final, to be flying a right turn with full left rudder, and large control inputs with the wheel. It's possible to have been in the right turn and needing nearly full left rudder and nearly full left aileron to stop the bank or decrease it, and any banking to the right would have resulted in more loss of performance. The crew may have been working the aircraft down to maintain directional control and prevent a stall; it's a fine line when already performance limited, with two engines out on one side.

As yet, not enough information is presented, as no clear indication is given as to the reason for the engine shut-downs. The fact that the propellers were feathered, or partially feathered, indicates deliberate engine shutdowns.

Don't give too much credence to a "bad mag." That saying is often used to describe a rough engine, and on a large radial, it can be difficult to tell if it's the magneto or fouled plugs. Most often, nearly always, it's fouled plugs as running 100LL in a large radial engine tends to lead to LOT of fouled spark plugs (lead and carbon). These short the plugs and lead to a rough engine. This is especially true of the lower cylinders. There are numerous possibilities that would produce engine roughness; determining a "rough magneto" on the initial climb would be nearly impossible, as it could be any number of things from a lifted cylinder head to fouled plugs, all of which are very common.

The problem occurred during the initial climb, when the engine is under the most stress; it's critical to thoroughly warm the engine for takeoff, but a radial engine has a lot more going on with it than other piston engines, with a lot more failure points. Operation on the ground with a rich mixture setting for any period of time can quickly lead to fouled plugs, and the pressure carburetors are highly susceptible to carburetor icing, especially at times of elevated humidity. Operation of carburetor heat, individually for each engine, is done on the ground and in flight. Rich settings for takeoff can lead to fouled plugs, which can produce very rough engines.

More information is needed regarding the cause of the shutdowns, but it's evident from the preliminary report that maintaining altitude was not possible and the aircraft was drifting down; it was unable to maintain adequate altitude until arrival at the runway. That's the meaning of the preliminary report. Anything more is as yet unknown.

sns3guppy...thank you for your continued input to this thread. I really appreciate your insight.

I'm learning things about the B-17 that I never knew.

For instance, I always thought an engine-out would not be a big deal for that bird. I guess that comes from watching war movies where they come back shot all to hell with half the engines not working.


...

Most of the time when an aircraft got shot up and made it back, it was drifting down from a higher cruise altitude. It also disposed of as much weight as possible, and generally as many of the crew as possible, too.

Most of the aircraft that got shot up didn't make it back.

A lot of mishaps and fatalities also happened in training: there was a very high attrition and loss rate in flight training, and crews arrived in theater with very little experience and very few hours: an absolute trial by fire.

Most of the policies and procedures, and much of what's known today about the aircraft, came at the expense of being written in blood: it was learned the hard way.

We are familiar today with turbine aircraft with very high thrust-to-weight ratios, and incredibly high mean times between failures. Many of the WWII era airplanes lasted short periods of time, and as the war bore out, couldn't be expected to last for long periods of time. Radial engines are heavy and produce very little power. While increased power is available, above which warbirds are typically operated today (we baby them because they're fragile and they break, and they're expensive, and they're old), two engines out on one side in this case would have meant full control deflection just to maintain control; increasing power may not have been possible because of the increased asymmetric thrust, and in fact, the crew may have needed to power back on the good engines. Catch 22.

Juan Browne's take on the prelim report. He does mention moisture in the magnetos, and so I may have been right in thinking the pilot said, "Blow the engine off" (although even he says "out").

He also confirms a low-drag approach using flaps up.

Moisture in magnetos?

How does one "blow the engine off" to remove "moisture in magnetos?"

Gear and flaps are electric. Only hydraulics are for brakes and cowl flaps. No engine driven hyd pumps as the pump is in the cockpit behind copilot near the bulkhead at the bomb bay. Wet mags are not unheard of and most operators have plumbed a line into the mags to blow nitrogen in them to dry them out. If they had two underperforming or shutdown on one side, it is doubtful they could make the runway from where they were especially at the speed and altitude they were at. Speed decay is eye watering from 1/3 to full flaps with 2 out on one side, so you better have a lot of airspeed and the field made before selecting more flaps. Time will tell. Sad day.

I was thinking of the 4Y (PB4Y) with the hydraulics, actually; wrong airplane.

I've never seen or used nitrogen to blow out a magneto on a large radial, but one would have no way of knowing or supposing that's the problem, given the more common issues with a large radial. Mag issues are a rarity, if they're maintained properly, and more so if pressurized.

quote:

14,000 hours for the captain, with no ATP indicates perhaps an ag background or something along those lines (it's unusual to get to 14,000 hours and not obtain an ATP). It's very possible that neither had been exposed to this type of event before.

7,500 hours of the Captains ~14,000 hours were time in type. He was the highest time in type active B17 pilot in the world at the time of the crash.

With two engines out and one partially feathered, downwind at 300', all the time in the world may not help if the performance isn't there.

Bit of thread drift. This is a current B17, repainted to match my uncle's B17, fired up 2 months ago.



They made it back in spite of 2 engines out (opposite side), one at 1/2 power...

Before the bomber released its bomb load, accurate flak shattered the Plexiglas nose, knocked out the #2 engine and further damaged the #4 engine, which was already in questionable condition and had to be throttled back to prevent overspeeding. Brown's straggling B-17 was now attacked by over a dozen enemy fighters (a mixture of Messerschmitt Bf 109s and Focke-Wulf Fw 190s) of JG 11 for over ten minutes.[15] Further damage was sustained, including damage to the #3 engine, which would produce only half power (meaning the aircraft had at best 40% of its total rated power available). The bomber's internal oxygen, hydraulic and electrical systems were also damaged, and the bomber lost half of its rudder and its port (left side) elevator, as well as its nose cone. Brown managed to fly the 250 mi (400 km) across the North Sea and land his plane at RAF Seething, home of the 448th Bomb Group.

ChuckFinley- I love reading stories like that. Thank You for posting it!

ChuckF - I know Ye Olde pub since I was a kid! Franz Stigler and the escort! This forum amazes me! Thank you.

Well, the hell with Collins Foundation. They got the plane from The Evergreen Aviation Museum in McMinnville Oregon last year.

First, they failed to tie it down prior to a windstorm resulting in tail damage.

Now, this.

It was a good bird, I walked thorugh her a few times. Regrete not going for a ride in her last year.

The Collings Foundation picked up the airplane in 1986.

Why "to hell" with them?

The airplane was damaged during a crosswind landing in 1987, and restored. It was also damaged in 1995 during a landing when it had a gear problem.

What are you talking about?

^^^^^^^^^^^^

Yeah, I walked through Nine O Nine 2 years ago. . .

Collings has owned that plane for decades.