Jump to content

PainGod85

Members
  • Content Count

    507
  • Joined

  • Last visited

Community Reputation

336 Excellent

1 Follower

About PainGod85

  • Rank
    Member

Profile Information

  • Gender
    Male

Recent Profile Visitors

1174 profile views
  1. PainGod85

    slow p47

    430 kph CAS at 9000 m in a standard atmosphere comes down to around 675 kph TAS, or 419 mph according to this online calculator: https://aerotoolbox.com/airspeed-conversions/ Without knowing how you calculated things, it's impossible to know why and how you ended up at 440 mph.
  2. PainGod85

    slow p47

    Speeds documented during flight performance tests are always in True Airspeed (TAS), that is, the speed of the plane through the air. Speed limitations are in Indicated Airspeed (IAS), as the only time IAS and TAS give you the same speed readings is at reference air pressure - at sea level. The further you climb, the more IAS lags behind TAS, as there's simply less air impinging on the measuring devices inside your pitot tube. However, IL-2 does not, to my knowledge, model instrument error, so what you see in the cockpit is actually Calibrated Airspeed (CAS), meaning measuring errors due to position error etc do not exist in the sim, so it's comparatively easy to tabulate actual TAS at any given altitude. (Strictly speaking this also means that flight limitations expressed in IAS need to have their error values added to actually arrive at IAS from the CAS displayed on the cockpit instruments.)
  3. I'll admit I've never tried.
  4. The intercooler's effects can be seen on the Carb. Air temperature scale on the right side of the pit. Open it to prevent charge air from exceeding maximum permissible temperature or risk detonation.
  5. Avialogs has the relevant TO: https://www.avialogs.com/aircraft-n/north-american-aviation/item/4781-t-o-01-60j-60-installation-of-accelerometer-p-51d-and-p-51h
  6. Actually, August 1944 is what T.O. 40-JE-8 is dated as, but the order itself refers to North American Service Bulletin 51-134, dated June 6. The well known photograph of the Bottisham Four formation of four P-51s, of which P-51D-5 44-13926 was fitted with a dorsal fin, is dated July 26, 1944. That said, the issue had been known since at least January 1943, when T.O. 1F-57A-6 was published, prohibiting deliberate spins in P-51 type aircraft until the cause of multiple structural failures had been found and rectified. In August '43, T.O. 01-60J-6 was released, relaxing some of the restrictions leveled on the P-51. T.O. 01-60J-6A, dated January '44, again placed restrictions on the type, this time against slow rolls at speeds in excess of 300 mph. T.O. 01-60J-6B followed the same month, with much the same content. T.O. 01-60J-6C, dated 6 June '44, references T.O. 01-60J-18. This is important as that order describes how to fit the dorsal fin fillet on P-51B and C type aircraft. It removes the flight restrictions by replacing T.O. 01-60J-6B upon the fitting of a dorsal fin fillet and anti-servo tab on the rudder. In fact, if you look closely, you'll see the first version of T.O. 01-60J-18 was published in April '44. Dorsal fins were added from the factory starting with the P-51D-10 production run. E: One more thing. Testing of the dorsal fin occurred no later than March 1944: http://www.wwiiaircraftperformance.org/mustang/P-51B_Stability_24march1944.pdf
  7. The main effects of slats is pushing the airfoil beyond what would usually be its critical alpha, and giving the wing a better lift to drag ratio at those higher angles of attack. Extending slats on an as yet unstalled wing naturally comes with a drag penalty for the same lift.
  8. Actually, if you look closely, it says that figures printed in red are preliminary. Granted, on a monochrome photocopy, a remark like that isn't satisfactory at all, but I don't think a tactical planning chart would consist of a majority of values that are asspulls. I'm trying to find a color copy of the same ATM, but I don't hold out much hope for finding one.
  9. The 109's LE slats deployed as a function of angle of attack. Pull hard enough and they will pop out at any speed, and at high speed, slat deployment naturally comes with a massive drag penalty as it substantially increases the airfoil's chord and therefore decreases the wing's aspect ratio.
  10. The V-1650-3 engine had a more aggressive supercharger gearing. Less power at low altitudes while increasing critical altitudes. This means comparing any two Mustangs with different engines is nonsensical in the extreme. With regards as to who screwed up...well, let's just say if the numbers don't conform to the following chart, there's a glaring issue with them: Also note that TK.589 was only subjected to what they called 'brief level speed trials'. Emphasis mine. That alone should be a red flag. E: Additionally, we do know TK.589 was a comparably old P-51D-5, original USAAF BuNo 44-13332. One could infer that some wear had already set in before delivery to the RAF.
  11. That Mustang IV test with TK.589 is extremely suspect. The plane achieved a measly 355 mph at SL and 67" / +18 PSI when it should've attained around 366 mph even with racks installed according to the type's SAC chart. At critical altitude for its first gear at 67", the plane is 16 mph slower than it should be with racks, at 396 mph compared to the 412 mph it should actually be achieving. This doesn't even factor in the fact the speeds attained with TK.589 were corrected to 9,000 lb, when the speeds I'm comparing it to are specified for a gross weight of 10,100 lb - so with a bit more induced drag. In fact, all Mustang tests performed by the British that I've seen show the planes as performing worse than they should, so my guess is there was a systemic error of some kind the RAE made when testing the type. E: Compare this to P-51D-15 44-15342, attaining 375 mph at 67" @SL, with racks. http://www.wwiiaircraftperformance.org/mustang/p51d-15342.html So yeah, either there's an issue with the RAE's testing methodology on the P-51, or TK.589 is probably the single worst P-51D ever performance tested by anyone.
  12. Both of those use BHP transcribed from the same chart. P-51B: P-51D: It's possible there's a transcription error in the P-51B report, and that for some reason they gave the power rating for the V-1650-3 at SL (or literally any other error you may think of). The plane itself obviously used a V-1650-7 as the trials were made to clear 150 grade fuel on that same powerplant, and to my knowledge there were no changes made to the engine that would result in this kind of discrepancy - which is a paper discrepancy in the end, with neither report actually measuring BHP produced by either engine. In any case, at low blower critical altitude the engine power is given as almost identical (a difference of a mere 5 hp), yet the P-51D remains faster by 8 mph. This is also not the only P-51B tested to those speeds: There is a point to be made how the P-51B's racks are draggier than the D's, with a corresponding speed reduction of 12 vs. 4 mph, but that would only give the former parity with the D, not superiority. By comparison the P-51D's racks had less drag when they weren't in use due to their ability to have their sway braces removed. I've heard 4 mph thrown around as the associated speed reduction, but so far I haven't found a hard source confirming that figure. E: The Tactical Planning Characteristics and Performance Chart for the P-51 does specify 12 and 4 mph speed reductions for the B/C and D, respectively.
  13. Nice pictures. However, I have one massive point of contention: Empirical data does not support this at all. P-51B, V-1650-7 engine, 67" MAP: http://www.wwiiaircraftperformance.org/mustang/p51b-24777.html Speed at SL: 361.5 mph At low blower critical altitude, 10.300 ft: 409.0 mph P-51D, same engine and settings: http://www.wwiiaircraftperformance.org/mustang/p51d-15342.html Speed at SL: 375 mph At low blower critical altitude, 10.000 ft: 417 mph This shows the P-51D, running the same engine with the same boost and turning the same prop as being faster than the P-51B, with both fitted with wing racks. This is with the P-51B only having four guns with ports covered, and having been stripped of paint whereas the P-51D report only specifies it was flown with full ammunition, implying the full six gun armament, and no mention whether its gun ports had been covered, or its skin stripped of paint. I will welcome any evidence to the contrary.
  14. 'Entwurf einer vorläufigen Motorenkarte 9 - 605 DB u. DC Ausgabe C Stand: 1. Dezember 1944' "Draft of a preliminary engine placard 9 - 605 DB and DC Edition C Status: December 1, 1944' Also: http://kurfurst.org/Engine/Boostclearances/DB_Niederschrift6730_DB605DBDC_20-1-45.pdf January 20, 1945 Further down, they lambast DB for even issuing releases of those boost pressures to Galland, citing a lack of a satisfactory results during testing with four of these engines. Additionally, they eventually compromise - towards the end of January 1945! - with continuing trials at 1.98 ata that had already begun with one group, and the continuation of trials with 1.90 ata until those engines failed, on the condition that engine replacements would be set to 1.80 ata.
×
×
  • Create New...