deaphen wrote:

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yup thats me alright bob! That was when i was in the states with my dad shopping for engines for his LR which is due in 2009. ;)after sweating my ass off all day in singapore! Got more pics of other engines up on mypicasa web... check them out.

regards
nitin

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With your dad i can understand.

Shopping for engines

For his LR

Due in 2009

Yaar I hope i got u right on the above.....

In my 5 years of Aviation i know only two LR's. One LR is Lapse Rate

Lapse Rates … A Review
A common way to evaluate degree of stability/instability for a layer of air is to compute the temperature difference between the bottom and the top of a layer and divide it by the thickness of the layer. This value is known as the observed Lapse Rate (LR).

In some layers, the measured temperature may be warmer at the top than at the bottom of the layer and LR is negative. This is a temperature inversion. If an inversion exists, stability conditions are always stable.

However, all stable layers aren’t necessarily inversions. If the measured temperature at the top of the layer is colder than the measured temperature at the top, LR is positive. The conditions may be either stable or unstable. Further evaluation is necessary.

We do this by determining what would happen to the temperature of a dry air parcel if it is raised from the bottom to the top of the layer … then released. In this process, the parcel starts out with a temperature equal to measured value (OAT) at the initial altitude. As our imaginary dry parcel moves upward, it cools as it rises because it expands due to decreasing pressure (adiabatic cooling). If, despite the adiabatic cooling, the parcel reaches the top of the layer with a warmer temperature than the air that is already there (OAT at the top of the layer), then the parcel is less dense than its surroundings and it will continue to rise on its own (unstable). On the other hand, if it reaches the top and it is colder (more dense) than its surroundings, it will sink back to its original level (stable).

The rate at which a parcel cools due to expansion is a constant value (3C/1000 feet) known as the Dry Adiabatic Lapse Rate (DALR). This fact makes the determination of stability easier than moving imaginary air parcels around. All we have to do to determine layer stability in dry conditions is compare LR with DALR. Since DALR is constant, this makes things pretty easy. If, in a dry layer, LR<DALR, the layer is stable; if LR>DALR, the layer is unstable. For example, if LR in a dry layer just happened to be equal to the lapse rate of the Standard Atmosphere in the troposphere (2C/1000 feet), the condition would be stable because LR<DALR.

Using lapse rates to evaluate stability in cloudy conditions is slightly more involved. It requires a comparison between LR and the Saturated Adiabatic Lapse Rate (SALR), rather than DALR. In clouds (RH=100%), a rising parcel cools more slowly because the adiabatic cooling is partially offset by the release of latent heat as water vapor becomes water or ice. Although SALR is NOT a constant value, generally, we can say that SALR is always less than DALR. Also, the value of SALR is close to DALR for very cold temperatures and much less than DALR for very warm temperatures. These variations reflect the large amount of water vapor (and therefore, latent heat) that can be present at the warmest temperatures. It follows that if we have two layers in the same altitude range with identical LRs, except one layer is dry and the other is cloudy, the cloudy (saturated) case is less stable.

To sum:

In dry conditions:
LR greater than DALR is unstable
LR less than DALR is stable

In cloudy conditions:
LR greater than SALR is unstable
LR less than SALR is stable

In both dry and cloudy conditions:
LR greater than DALR is always unstable
LR less than SALR is always stable

The degree of instability (-) or stability (+) is proportional to the magnitude of the difference in lapse rates.

Or does LR mean one of those LONG RANGE engines.....

Cos if it is then you guys should know this that : SQ was offered a deal for 12 B777-200/LR's back in 1997.,but turned down the offer as they were simply not convinced that the B777-200/LR does not meet its payload/range requirements between SIN-LAX all year round. SQ wants to carry at least 206 pax over a still-air range of 16,260kms , but is also stipulation an extra 60mins. of fuel for airport diversions, hold and go-around. SQ is also factoring in fuel deterioration and a 2% empty-operating-weight penalty. Boeing has raised the MTOW to 340,000kgs, and added auxiliary belly-fuel tanks, in an effort to meet SQ's demands. SQ finds that the aircraft still falls short of between 11 & 95 pax at different times of the year on the LAX to SIN portions.

Does your father work for an AIRLINE