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[1.99.1.54] Tempest Mk II has poor high-speed handling


ISSUE: Tempest Mk II suffers from poor high-speed handling, especially when compared to the mk V.

Game mode: RB, perhaps SB as well.

How to replicate: Take the Tempest Mk V and Mk II to speeds above ~600kph, and execute hard turns and/or other maneuvers. If logging statistics, compare max G pull and elevator deflection at high speeds.

 

Within Tempest II Tactical Trials, many of the characteristics of the Tempest II are noted.

Quote

The general impression is that the Tempest II handles better that the Tempest V.

When entering the section titled "Tactical Comparison" with Tempest Mk V, the comparison becomes more specific, discussing the capabilities of each aircraft, and differences in what they are capable of doing.

 

Notable, however, is point 49. 

Quote

Dive

49.            The two aircraft are identical.

 

However, this does not line up at all with the in-game behavior, where the Tempest II is substantially less responsive in dives, locking up severely at high speed when compared to the Mk V.

 

I performed a test flight (.clog attached) in both aircraft, taking a constant 20 minutes of fuel on spaded aircraft, took each aircraft to 2500m, then entered a 30 degree dive, immediately using max elevator as 800kph was reached, and not releasing, instead completing multiple loops until speed at the top of the loop was roughly equal with the past loop. Using WTRTI's logging capability along with Excel, data for near-identical conditions was acquired, and a side-by-side comparison was graphed. The graphs may be seen below. From this it is evident that the Mk II pulls fewer Gs across the board, but above 600kph this becomes particularly pronounced, which in-game severely hampers the Mk II's ability to make high-speed attacks. While the Mark II does reach a higher speed than the Mk V, this is because the Mk II's worse compression makes it take noticeably longer to pull out of dives at high speed, even relatively shallow ones.

Spoiler

IASvsElevator.thumb.png.97071bc29023e595IASvsG.thumb.png.4146eeca9ec473d98726f78

Did another test to check with flat turn capability, these are the results: (line is a little squiggly because I had to constantly adjust roll to try and keep the turn flat)

image.thumb.png.20f4c3517bda0b6bb2323f66

 

 

While the Tempest II does have a slightly higher stall speed, which (given the similarities of the wings and airframe) would reasonably result in a slightly lower G pull for any given speed, the issue becomes markedly more severe at high speeds. (As an aside, it seems both Tempests are underperforming in the stall speed department. Another report will on that has been submitted can be expected soon.) If the issue was consistent, that would make sense, but it becomes quite severe in dives/at high speeds, which is where the aircraft were explicitly stated to be identical.

 

The documents for the Tempests note that the elevator remains effective throughout the speed range, and is moderately light and adequate for all flight except power-off glide landings (where it begins to run out of authority).

Spoiler

Tactical Trials: 24.            The elevator control is moderately light and is adequate for all flying except as previously stated in a glide landing. Changes of speed and power have less effect on the trim of the aircraft than on the Tempest V or other contemporary British fighter.

 

Mk V manual:

image.png.1a38eaa9cfc04fec18c30f32103f72

Mk II Manual: (unfortunately section II of general flying does not discuss the controls, but skips directly to trim behaviors)

image.png.d33cba8a51f001694785cd3db87da3

Additionally, the manuals for both the Mk V and Mk II note that the elevator trim controls are very sensitive in dives/at high speeds.

Spoiler

Mk V manual:

image.png.35833d97e90d041e1f631a964f3b5b

image.png.7a817bbfc5b38092ed482a046742ee

Mk II manual:

image.png.b6ca203090fa8e91da974f342c6aa3

 

It is of note to mention that while the Mk II has a nose-heavy dive and the Mk V has a tail-heavy dive, neither advise trim in dives, due to the high sensitivity of the trimming apparatus. Given that the Tempests use a conventional trim tab and not an adjustable horizontal stabilizer (like 190s and 109s did), the authority of the trim mechanism is closely linked to main control surface authority. (Indeed, instructions for dive recovery explicitly state that if one enters the compressibility range/encounters Mach tuck, to NOT use the trim tab, as when one gets back into non-compressibility region, the sudden responsiveness of the tabs may result in excessive pullout force. This demonstrates the link between the authority of both the main control surface and the trim control surface.) 

Spoiler

AFDU Report #116:

image.png

 

(This document also states that the Tempest "feels more solid and easier to control than most aircraft at speeds over 400 I.A.S." This is speeds in excess of 653kph, yet the Tempests suffer from large amounts of compression at such speeds, far less than many contemporaries in war thunder)

 

This would seem to indicate that until you hit Mach tuck, IRL both aircraft had very effective elevators. (If the elevators were not effective, then trim tabs would also not be so effective, and would be recommended or required to pull out of high-speed dives, rather than being forbidden in high speed dives) Given that source documents note excellent handling and/or control authority until the Mach Limits of the aircraft (.77M), it seems like the Tempests may be suffering from excessive IAS-based elevator compression. This is particularly noticeable on the Mk II. As noted above (IAS vs elevator % graph), the Tempest II and V elevator deflections begin to converge at ~575kph, and are essentially the exact same from 610kph on up, leaving the Mk II anywhere from .5 to 1G behind. Due to the way the Tempest II is modeled, it needs to use more elevator at any given speed to reach a given load factor. Thus, while the effects of compression aren't seen on the Mk V until ~615kph, they can be seen as early as ~590kph on the Mk II. When this is combined with the overall lower pull of the Mk II, it results in an aircraft that is noticeably worse when trying to make high-speed attacks. (Again, the slightly higher stall speed of the Mk II would make it slightly less maneuverable across the speed range, but the issue become less severe at high speeds, because when that's where the aircraft are noted to be identical, but in-game it is currently more severe at high speeds.)

 

Spoiler

EDIT: Furthermore, I've looked into a few other aircraft, and found some interesting results. The FW190D-9 and F-8 will both pull ~8Gs at 600 (better than the Mk II, slightly worse than the Mk V), and have the same approximate elevator deflection as the Tempests until 600kph, where the Tempest will comparatively plummet. By the time you reach 800kph, the Tempest's deflection is under 20% while the Dora is at 42%, and the max G of the Mk II is 5G, less than half of the 190s' 11Gs.

image.thumb.png.0bc2448aada27e8e6aef2c46

image.thumb.png.d32230dbd9c40dc7aaadffeb

image.thumb.png.aa8d7672eb1d7d452cc7b15e

At 750kph, the Tempest's deflection is comparable to the K-4 (though they require different amounts, so this matters less.)

 

The main point here is that the 

image.thumb.png.3e5d2f603228fc6a48562151

Particularly of interest is the 109K-4 vs Tempest comparison. Despite the latter being designed for high-speed maneuverability, it falls at a distinct disadvantage in game at high speeds. If one graphs the K-4 max G vs IAS, it not only is higher than the Tempest for all speeds (despite the IRL tactic of Tempests to keep engagements with 109s above 250MPH so they could maintain a maneuverability advantage over the 109), but the rate at which maximum G pull is lost is nearly identical, with the Tempest beginning to compress before the K-4.

image.thumb.png.efe96edcc676df9aa861ac6e

 

While one could argue that the VNE of the Tempest II was lower, and thus it should have worse compression, it also had a different pitot tube, and thus a different PEC. As a matter of fact, the PEC trends are the exact opposite of each other, and end up all but cancelling out at the point of VNE. Furthemore, it was noted in tests that they performed/handled identically in dives.

Spoiler

Mk V PEC:

MkVPEC.png.93845e436ee39ac6847ac5c62a973

Mk II PEC:

MkIIPEC.png

Graph of PEC trends: (correction points graphed at the midpoint of the range for each)

image.thumb.png.70830d2eb0dbfbda2890e84a

One can clearly see that if one extrapolates the trends out, the IAS VNE limits become very close to each other.

 

SUGGESTED FIX: Improve high-speed handling of the Tempests such that the Mk II is equal in high-speed dives to the Mk V, and such that the Tempests don't fall far behind aircraft similarly noted to have excellent high-speed maneuverability, such as the FW 190.

2020_07_26_14_27_11__16472.clog

DxDiag.txt

Edited by DJBscout
General phrasing and clarification
medal medal medal

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Hi.

 

I had the devs to review the claims.

 

Current behavior of Tempest, based on your data and what Gaijin has (which is pretty much the same) is not conflicting with the current implementation.

 

Mk II has a higher stall speed than the V, which reflects the different on the left part of your plotting.

Mk II need more elevator "up" to keep nose from falling, white MK V needs more nose down. That means that due to weight and balance and CoG/CoL, the Mk II cannot pull as many G as the V.

 

Based on your testing, the tempests can do 5G at maximum speed / VNE; which is about human capabilities. No pilot would ever complain of a 5G capabilities at VNE. Standard recovery is generally made around 2-3G.

Also, you analysis on the elevator trim is a double edged sword. It could be interpreted as that the forces on the stick due to the trim exceed the force provided by the pilot. That makes trimming very efficient and dangerous, while the pilot would be "stick locked" due to aerodynamic forces.

elevator effectiveness and pilot capabilities to deflect are two different matters.

 

Regards

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