|Quoting WarrenPlatts (Reply 149):|
To get from IGARI to the radar track, you need a ground speed of at least 500 knots.
Very pessimistic estimate
Tough indeed. Somebody wanted to escape fast. Maybe with some bravado a la Tex Johnston.
Actually only higher than 21,000ft (see below)
|Quoting tailskid (Reply 154):|
a 777 could not fly IGARI - Penang - MEKAR with a descent to 5,000 feet or so and make it to MEKAR by 2:22
Could not but in the following revised scenario flying down to 5,000ft may not be necessary.
To explore the piloted scenario, I keep the portion of the track around Penang as shown in the Prelim. Flying IGARI to Penang and descending was probably part of the plan to simulate a commercial flight with a transponder problem. In case anyone was watching, that target would be classified as friendly. In my original 4 step scenario, I had assumed 5,000ft or below to use terrain masking but that would burden the time budget too much as pointed out by Pihero.
In the Penang area, I now assume that two radars were involved rather than only one in my original scenario:
- one radar on Butterworth AB
, essentially at sea level (20m?). I could not find the type and model of that radar. I assume that this radar is used for approach control and has a limited range.
- one radar on Pulau Pinang. It is a Selex Sistemi Integrati RAT-31 DL
/FADR (installed as a Fixed Air Defence Radar). It is a modern(NATO) phased array radar with an 11x7m antenna operating in L-band. Located on the highest point of Pulau Pinang at an elevation of approx.2,700ft it has a 250nm range and potentially 360 deg coverage. GE
shows that it is protected by an 18m dome and that is exactly the advertised value for its radome size. It can be controlled remotely as the SOC is installed at Butterworth AB
My current hypothesis is that the Butterworth radar is responsible for the portion of the radar plot, east of the white circle. I estimate that the a/c emerged from the projected shadow of Pulau Pinang at an approx altitude of 13,000ft. It is not clear why the a/c radar returns became infrequent before the white circle. Most likely the a/c fell below the radar horizon i.e. flew below 11,000ft but the Butterworth radar may also have a range limitation (maybe due to power limits and a higher PRF). Anyway, at 02:07:16 Butterworth radar loses contact.
When the Butterworth radar started detecting the unidentified track on radial 275, I think that the more powerful Pinang radar was off. If it had been on, it should have detected the a/c earlier, unless its coverage sector in azimuth was restricted for some operational reason (normally the antenna rotates at 6 to 10 rpm). At some point the Butterworth operators decided to start the Pinang radar. A few seconds after 02:13, the Pinang radar became operational and picked up the a/c. We do not the a/c altitude at that point (although the investigators should since RAT-31DL
is a 3D radar). All we know is that the a/c must have been flying at or above 7,000ft.
At 02:22, the last primary radar contact occurred 240nm from Butterworth AB
, the a/c altitude must have been at least 21,000ft.
As we can see, the two radar hypothesis allows the climb west of Penang to have been performed at a high CAS
because the climb angle may have been very shallow (e.g. 0.6deg) and the T7
weighed at only about 74% of its max weight. There is plenty of power left in those engines and since ACARS had been stopped from transmitting, RR
will never know how long max continuous thrust may have been used. Of course in such a scenario, fuel economy is totally disregarded in that phase of the flight .