BAe146 Landing Distance
Thread Starter
BAe146 Landing Distance
I'm wondering if someone on here is intimately familiar with how the BAe146 landing performance data was obtained.
Looking in the FCOM there is a small variation in landing distance required for different 146 variants at the same weight. A BAe146-100 requires about the same amount of runway as a -300 with no wind, more runway with a tailwind, and less runway with a headwind. This is all at the same weight. Example:
The difference is relatively small but it is there and it is consistent. It seems that for the same weight, a BAe146-100 is more affected by wind than a larger -300. The aircraft are nominally identical aside from fuselage length. Same engines, same wing, same frontal area etc.
The question is, how is the data obtained and is there a reason why the smaller 146 is more affected by wind or is it just the result of minor variations in flight testing?
Looking in the FCOM there is a small variation in landing distance required for different 146 variants at the same weight. A BAe146-100 requires about the same amount of runway as a -300 with no wind, more runway with a tailwind, and less runway with a headwind. This is all at the same weight. Example:
Code:
Type | Weight | 15 knots TW | 0 wind | 40 knots HW |
| | | | |
-100 | 33,000 kg | 1700m | 1220m | 890m |
-300 | 33,000 kg | 1620m | 1220m | 920m |
The question is, how is the data obtained and is there a reason why the smaller 146 is more affected by wind or is it just the result of minor variations in flight testing?
Thread Starter
It's the wet chart, sea level, zero slope. The graphs give the same answers. They are rounded to 10s of meters but the difference is more than the rounding error.
Aero, the table suggests that this is a computer print out opposed to the FCOM (although the manufacturers FCOM was rewritten some time ago). Data prints could be supplied by any service provider.
Also, the 15kt tailwind clearance was not universal for all operators; Australia was one of the first clearances and the distances were almost certainly a cautious extrapolation of existing data.
Tabulated computer data was based on the AFM charts, and had to demonstrate sufficient agreement such that there were no significant differences. This may have involved data points every 20m erring on the safe side of the line. Thus the landing distances were within a cricket pitch length on the safe side of a pencil line over the AFM.
AFM performance was based on a more accurate manufacturers computer model of aircraft performance. This model would be use a set of actual landings, in a limited range of conditions, as agreed by the regulator, averaged across at least five pilots with five landings each, etc, etc, and adjusted with additional time margins and factoring required by regulation. There would be few actual actual approach and landings as the data was an assembly of each phase; i.e. flare and touch down, then separately deployment of landing devices and commencement of braking, and then brakes on to a full stop. Actual approach and landing distances may only have been a spot check, as with wet data, which is normally based on extrapolation - hence the caution required in very wet conditions.
The 146-100 and -300 data were flown over a range different tests and locations, several years apart and possibly biased towards the market for each type, e.g. the -300 at higher weights. Some Australian aircraft had the updated 507-1h engine but I would not expect this to change landing performance.
Thus the differences in the data might only reflect the range of variables in collecting, preparing, and publishing performance, but always erring on the safe side w.r.t. the AFM; but this still requires human judgement of actual conditions and similar bias towards a safe margin.
P.S. Carbon or steel brakes? I cannot recall any differences; but there were for high / low pressure tyres.
IIRC, distances were measured in ft, but published as required in meters.
Also, the 15kt tailwind clearance was not universal for all operators; Australia was one of the first clearances and the distances were almost certainly a cautious extrapolation of existing data.
Tabulated computer data was based on the AFM charts, and had to demonstrate sufficient agreement such that there were no significant differences. This may have involved data points every 20m erring on the safe side of the line. Thus the landing distances were within a cricket pitch length on the safe side of a pencil line over the AFM.
AFM performance was based on a more accurate manufacturers computer model of aircraft performance. This model would be use a set of actual landings, in a limited range of conditions, as agreed by the regulator, averaged across at least five pilots with five landings each, etc, etc, and adjusted with additional time margins and factoring required by regulation. There would be few actual actual approach and landings as the data was an assembly of each phase; i.e. flare and touch down, then separately deployment of landing devices and commencement of braking, and then brakes on to a full stop. Actual approach and landing distances may only have been a spot check, as with wet data, which is normally based on extrapolation - hence the caution required in very wet conditions.
The 146-100 and -300 data were flown over a range different tests and locations, several years apart and possibly biased towards the market for each type, e.g. the -300 at higher weights. Some Australian aircraft had the updated 507-1h engine but I would not expect this to change landing performance.
Thus the differences in the data might only reflect the range of variables in collecting, preparing, and publishing performance, but always erring on the safe side w.r.t. the AFM; but this still requires human judgement of actual conditions and similar bias towards a safe margin.
P.S. Carbon or steel brakes? I cannot recall any differences; but there were for high / low pressure tyres.
IIRC, distances were measured in ft, but published as required in meters.
Thread Starter
safetypee, thanks for the info. The table in my post is just my own formatting of the original tables from the latest version of the -100 and -300 FCOM Vol 3 Pt 4 (Flight Deck Handbook). 502 engines for the -300, not 507. I was not flying the type prior to the major FCOM rewrite, I understand the old "MomVol's" were far less user friendly.
The graphs from the flight manual show straight wind lines which would suggest to me that there is no additional factor for the 15 knot column. We also have data for 20 knots tailwind, that does have an additional 10% factor.
The FCOM tables and flight manual graphs include a 67% safety factor so any variations in the original flight test data would be magnified by a similar amount.
Brakes and tyres are carbon and high pressure for both types.
From what you say about how testing is done, I'm thinking it's most likely just a result of minor variations in flight test results.
The graphs from the flight manual show straight wind lines which would suggest to me that there is no additional factor for the 15 knot column. We also have data for 20 knots tailwind, that does have an additional 10% factor.
The FCOM tables and flight manual graphs include a 67% safety factor so any variations in the original flight test data would be magnified by a similar amount.
Brakes and tyres are carbon and high pressure for both types.
From what you say about how testing is done, I'm thinking it's most likely just a result of minor variations in flight test results.
Thread Starter
It's the same mass. The numbers are for 33000 kg for both aircraft (about max landing weight for the -100 and mid to light landing weight for the -300.)
