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Another factor to consider is that Mogas vaporises much more readily than Avgas, as used to be demonstrated by pouring a thimbleful of each on a concrete floor. An even better demonstration is to prove how easily it vaporises in an ultralight fuel pump during a long climb with no electric pump backup. I still have the scars from the ensuing forced landing :ouch:
Always sad to hear of any accident particularly when this should have been a joyous and much anticipated aviation occasion. My sympathies to the families of those who lost their lives. |
"For the motor octane number when you reach 100% isooctane you cant of course mix more isooctane"
By definition the octane rating of isooctane is 100. Both 100 RON and 100 MON, with RON meaning Research Octane Number and MON - Motor Octane Number. These tests are done on 2 different types of Octane engine. The MON rating of a particular fuel is always lower than the RON rating of the same fuel. This is because the MON method is a harsher test on the fuel than the RON method. There are plenty of fuels that have an octane number greater than 100, both MON and RON. By "fuel" I'm not meaning necessarily commercially available fuels but any hydrocarbon that can be successfully run on the laboratory internal combustion engines. "I’ve heard the ”Performance number” before but as often Ive also heard octane numbers above 100." Octane numbers refer to fuels tested on normally aspirated laboratory engines (F1 or F2) while Performance Numbers refer to tests performed on a supercharged laboratory engine (F4 engine). So 3 different types of tests, 2 types of Octane number, 1 Performance Number. All 3 can be greater than 100. Performance Number - always, MON - always for Avgas, not for motor gasolines, RON - never for regular commercial fuels (Avgas is not tested on the RON engine but it would be higher than 100) but Toluene for example is over 120 if my memory is correct.. |
I’ve heard the ”Performance number” before but as often Ive also heard octane numbers above 100 https://cimg9.ibsrv.net/gimg/pprune....52c12e2ec5.jpg |
Originally Posted by megan
(Post 10602773)
As I said, for ratings above 100 the community has adopted the word "Octane", but technically it's not correct. Octane rating of a fuel is one that has the same knock characteristics of a particular mixture of iso-octane and heptane. 90% iso-octane and 10% heptane has an octane rating of 90. Pure iso-octane ie 100%, has a rating of 100 octane. With a fuel that has better knock characteristics than 100% iso-octane they obviously had to come up with a means of quantifying the knock rating, hence the "Performance Number". As you can see from the chart both lean and rich ratings are given as PN ("Performance Number") because both are above 100, though they seem to have transposed the rich and lean numbers. Once again, technically 100 is as high as an octane rating can go. I must emphasise the word technically ie the petroleum industry, not community common usage.
https://cimg9.ibsrv.net/gimg/pprune....52c12e2ec5.jpg Perhaps I wasn't clear enough in my previous post. The 100/ 130 bit in Avgas 100/ 130 for example refers to 2 different test results using 2 different engine types. The 100 number is an Octane number in this case a MON (Motor Octane Number) obtained by testing the fuel on a MON engine, method ASTM D 2700. The 130 number is a PN (Performance Number) determined on a F4 Supercharged engine, method ASTM D 909. The 2 engines are quite different, the methods are very different as are the results. One is an Octane number, one is a Performance Number. When running a MON test on an Avgas sample the result is always over 100 because the 100/130 bit refers to a minimum spec of 100. The reference fuels over 100 required for the test are prepared by adding TEL (tetra ethyl lead) to isooctane. There is an error in that Shell info sheet. The method is ASTM D 909, not 910.. |
Hey posters, are we good with the discussion about octane rating on this thread now? Good discussion, though a little off topic here. We can do a separate gasoline thread if you like, good info, but probably not really relevant to this accident...
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An interesting Liberty Belle cockpit overview by one of the B-17 pilots - dated 2011 but a couple of interesting points
1) Landing gear 45-50 seconds to fully retract or extend 2) Significant drag from cowl flaps - sometimes used to assist in trimming/turning the aircraft as in high crosswind. 3) Lands fine with flaps retracted 4) Good discussion on the prop feathering buttons and relationship to pitch control - interestingly mentions that in the event the prop feathering system failure for an engine out, pitch control was the only option to turn the blades at least partially. Curious that he would mention prop feathering failiure in discussion of pitch levers. Several posts on other sites indicate feathering problems or inability to feather engines on the early G models due to the removal of the oil tank standpipe as part of weight saving measures. I have not been able to confirm and no source given. Anyone? |
Originally Posted by Pilot DAR
(Post 10603506)
Hey posters, are we good with the discussion about octane rating on this thread now? Good discussion, though a little off topic here. We can do a separate gasoline thread if you like, good info, but probably not really relevant to this accident...
Cheers, Grog |
I posted a B-17 training film from the 40’s. Im pretty sure the instructor tells the trainee to limit manifold pressure as they’ve “got 92 today”. |
In one of the videos the pilot mentions that the guy who put the throttle levers the way the are on the B-17 should be hung up and I agree. Wonder if it was the same guy who put the mixture levers with rich in the aft position. Hope they pull the cord 1mm/day once its tense.
LG switch, geeee. Putting all 4 feathering buttons together. Better separate left from right wing ones like on the DC-6 and others I feel. Must have been a very good aircraft to do its job but the cockpit controls deserved a better design/set up. |
I suspect an overwhelming majority of the 400 hour pilots that flew the B-17 in combat didn't have an issue with the cockpit layout, considering it was the only four engine aircraft they had ever flown.
The throttles were designed that way to provide simultaneous control of one side or of all four engines in one movement. Adjustments had to be made often to keep the aircraft in the tight combat box formation. |
Originally Posted by ThreeThreeMike
(Post 10604307)
I suspect an overwhelming majority of the 400 hour pilots that flew the B-17 in combat didn't have an issue with the cockpit layout, considering it was the only four engine aircraft they had ever flown.
The throttles were designed that way to provide simultaneous control of one side or of all four engines in one movement. Adjustments had to be made often to keep the aircraft in the tight combat box formation. The good thing is that it raised investigation and evolution. -- QUOTE control of one side Guess you meant outbord or inboards. Don´t recall having any problem flying formation with the DC-6 using its ergonomic throttle levers setup |
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No a nice reading ..
My sincere sympathy to the families of the B17 crew of that flight when they will be reading this PS : .I am not forgetting the families of the pax that died in that accident , but the difference is they they wanted and expecting a special experience when boarding that flight because it was out of the ordinary and flown by enthusiasts and volunteers. Sometimes **** happens in those conditions , No-risks heritage flying does not exists. . |
I wonder what the maintenance discrepancies were. That could be a big issue if they were significant and especially if they led to the accident.
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Originally Posted by tcasblue
(Post 10728912)
I wonder what the maintenance discrepancies were. That could be a big issue if they were significant and especially if they led to the accident.
As someone that has flown with Collings on 2 occasions some 10+ years ago, the report details makes sad reading. |
Originally Posted by tcasblue
(Post 10728912)
I wonder what the maintenance discrepancies were. That could be a big issue if they were significant and especially if they led to the accident.
Condition and Limitation No. 6 states as follows: Collings must maintain all aircraft subject to this exemption in accordance with the— a. Collings General Maintenance Manual; b. Maintenance requirements as specified in the appropriate type specification sheet, as amended; c. FAA-approved maintenance inspection program that meets the requirements of § 91.409(e), (f)(4), and (g); and d. Appropriate military technical manuals. Inspection of the engines on the B-17G N93012 established magneto and ignition failures existed. Regarding engine 4, to prevent the magneto “P” leads from separating from the magnetos, someone had attempted to rig the magneto leads in place with safety wire. Inspection and testing of engine 4 left magneto revealed the movement of the safety-wired lead caused grounding to the case, which rendered the magneto lead inoperative. In addition, the right magneto of engine 4 was found unserviceable. The cam follower was worn beyond limits and the point gap was less than half the measurement required by service documents. When tested, the magneto produced weak or no spark to four of the nine cylinders. All spark plugs were inspected and required cleaning and all electrode gaps were out of tolerance; therefore, further engine inspection indicated signs of detonation and associated damage. An inspection of engine 3 showed all spark plugs electrode gaps were out of tolerance, fouled, and revealed various signs of detonation. Further inspection of this engine revealed problems with the cylinders. As a result of these findings and other information, the FAA questions whether the engines were inspected adequately and in accordance with the applicable maintenance requirements. The discrepancies noted above indicate maintenance, or lack thereof, occurred in a manner contrary to maintaining aircraft in accordance with the General Maintenance Manual (GMM). The GMM incorporates by reference inspection procedures for individual aircraft, as described the Aircraft Maintenance Manuals. See General Maintenance Manual Rev. 1.1 at 19 (Sept. 10, 2017). Moreover, the records memorializing the inspections and maintenance performed on the B-17G lack key information and, in some cases, indicate maintenance was either not performed at all or was performed in a manner contrary to the applicable requirements. See Ground Check Inspection Form #15: Accessory Inspection, Engine Number Four Fourth (25 Hour) (Sept. 23, 2019); Ground Check Inspection Form #17: Ignition System Inspection, Engine Number Four Fourth (25 Hour) at ¶¶ 11-13 (Sept. 29, 2019). In addition, maintenance records indicate the removal of wires and no further repairs or adjustments, even though a wire was burned and arcing. See NL93012 B-17G Flying Fortress Flight Report (May 11, 2019). The same record, as well as a record from the following day, indicates flights with passengers occurred in the aircraft. See id.; NL93012 B17G Flying Fortress Flight Report (May 12, 2019). As a result, Collings did not fulfill the requirements of Condition and Limitation No. 6. |
Thank you for this information. Very interesting and also concerning. I find the information that the pilot in command was also the Director of Maintenance most concerning as presumably he is and was responsible for all the other aircraft within the maintenance organisation. An unacceptable conflict of interests in my opinion . I have been a director of maintenance here in Canada and cannot imagine ever being in this position.
very sad. |
Originally Posted by WING7
(Post 10604535)
Make no mistake TTM, those pilots had throuble with the cockpit layout and controls. Raising the gear instead of the flaps upon landing is a biggie.
The good thing is that it raised investigation and evolution. -- QUOTE control of one side Guess you meant outbord or inboards. Don´t recall having any problem flying formation with the DC-6 using its ergonomic throttle levers setup It was because of the study of many aircraft mishaps, including B17 gear selection mistakes, which lead to changes in cockpit design and the birth of ergonomics.One result was control selector standardisation,landing gear selector with a wheel shape and flap selector with an aero foil section. |
Originally Posted by ATC Watcher
(Post 10728886)
I am not forgetting the families of the pax that died in that accident , but the difference is they they wanted and expecting a special experience when boarding that flight because it was out of the ordinary and flown by enthusiasts and volunteers. Sometimes **** happens in those conditions , No-risks heritage flying does not exists.
. I have flown in the B17 Fuddy Duddy several times and I have to say that not once on any of these occasions, regardless of a/c type, did it ever occur to me to consider anything as banal as insurance. I agree with ATCW; people who subscribe to these flights generally regard them as an adventure which, by definition, involves the excitement of something daring or potentially risky. If they wish to remain totally safe (and "totally" is relative!), they should stay in the car park and give up their seat to someone prepared to accept and enjoy these flights for what they are. Of course, I'm not condoning improper maintenance or operational procedures, but those are different subjects. |
Originally Posted by Gipsy Queen
(Post 10729172)
I have flown as pax in many heritage aircraft and am sufficiently heritage myself to have piloted some of them commercially, years before they became "heritage"!
I have flown in the B17 Fuddy Duddy several times and I have to say that not once on any of these occasions, regardless of a/c type, did it ever occur to me to consider anything as banal as insurance. I agree with ATCW; people who subscribe to these flights generally regard them as an adventure which, by definition, involves the excitement of something daring or potentially risky. If they wish to remain totally safe (and "totally" is relative!), they should stay in the car park and give up their seat to someone prepared to accept and enjoy these flights for what they are. Of course, I'm not condoning improper maintenance or operational procedures, but those are different subjects. |
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