Narrative:

Cleared for the ohsea 1 RNAV arrival for runway 20R; with visual approaches in use. Crew elected to load the RNAV Z 20R approach for vertical and lateral reference; but later executed an ILS to 20R due to deteriorating weather conditions at the field.first issue:during preflight planning; crew determined using the lax 127 degree radial and elb 227 degree radial in fix pages 1 and 2 to reference the lax class B airspace structure (lax 10-1B in sna reference pages). Crew noted that the way point constraints on the RNAV rnp Z runway 20R (sna 12-21) for mnnie and klipp were 210 knots or less; which matches the depiction on the approach plate (ball note 1:210 knots maximum at mnnie and klipp). However; using the fix pages above; the crew determined that both these points are under the lax class B airspace; and therefore under far 91.117; the maximum speed for these points is 200 knots.as recommended in departure arrival note 2; crew placed a hard speed constraint of 200 knots at laxbb; and changed the speed constraints at mnnie and klipp to 200B (less than 200 knots) to comply with far 91.117. However; it is extremely disconcerting that the approach plates and the database is coded to allow for a direct violation of far 91.117; and that direct manual intervention is required preclude a violation of far's.second issue:during the descent phase of the flight; flight was on profile and speed with LNAV and VNAV path. Passing sippp intersection; ATC directed 'after tandy; proceed direct to kaynn and descend via the remainder of the ohsea 1 arrival.' crew complied with modifying the legs page; and after tandy; the FMS vertical path showed a sudden and considerable deviation above path. The pilot flying immediately engaged full speed brakes with idle thrust; which resulted in a 2600 FPM descent rate. Passing 11;000 ft MSL; PF (pilot flying) began to shallow the descent rate to get below 250 knots at 10;000 feet; and directed the pm (pilot monitoring) to advise ATC that we would not be able to comply with the kaynn restriction due to the shortcut. The controller directed the flight to 'maintain the current rate of descent to cross kaynn at 7;000 feet'; with the obvious implication that ATC didn't care about the speed but the altitude. The crew interjected that we were unable to exceed the maximum speed limits below 10;000 and below the lax class B airspace. The controller soon switched the flight to another sector; with the discrepancies never being addressed. While the above issue regarding the published arrival was disconcerting; this captain finds the apparent disregard of this controller for far 91.117 absolutely alarming. This controller clearly has no idea that the laws of physics are not negotiable; and that what he was asking this crew to do; in the time and space allotted; was simply not possible while remaining in compliance with basic far restrictions; and when the crew voiced their concerns; the controller was unwilling to even acknowledge their concerns.the next time this captain encounters these kind of ATC directions; he will be more directive and state in explicit terms: unable to comply.

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Original NASA ASRS Text

Title: B737 flight crew reported being given an instruction that would violate a FAR regarding speeds below a LAX Class Bravo airspace.

Narrative: Cleared for the OHSEA 1 RNAV arrival for RWY 20R; with visual approaches in use. Crew elected to load the RNAV Z 20R approach for vertical and lateral reference; but later executed an ILS to 20R due to deteriorating weather conditions at the field.First Issue:During preflight planning; crew determined using the LAX 127 degree radial and ELB 227 degree radial in FIX pages 1 and 2 to reference the LAX Class B airspace structure (LAX 10-1B in SNA reference pages). Crew noted that the way point constraints on the RNAV RNP Z RWY 20R (SNA 12-21) for MNNIE and KLIPP were 210 knots or less; which matches the depiction on the approach plate (Ball note 1:210 knots maximum at MNNIE and KLIPP). However; using the fix pages above; the crew determined that both these points are under the LAX Class B airspace; and therefore under FAR 91.117; the maximum speed for these points is 200 knots.As recommended in Departure Arrival note 2; crew placed a hard speed constraint of 200 knots at LAXBB; and changed the speed constraints at MNNIE and KLIPP to 200B (less than 200 knots) to comply with FAR 91.117. However; it is extremely disconcerting that the approach plates and the database is coded to allow for a direct violation of FAR 91.117; and that direct manual intervention is required preclude a violation of FAR's.Second Issue:During the descent phase of the flight; flight was on profile and speed with LNAV and VNAV Path. Passing SIPPP intersection; ATC directed 'After TANDY; proceed direct to KAYNN and descend via the remainder of the OHSEA 1 arrival.' Crew complied with modifying the legs page; and after TANDY; the FMS vertical path showed a sudden and considerable deviation above path. The pilot flying immediately engaged full speed brakes with idle thrust; which resulted in a 2600 FPM descent rate. Passing 11;000 ft MSL; PF (Pilot Flying) began to shallow the descent rate to get below 250 knots at 10;000 feet; and directed the PM (Pilot Monitoring) to advise ATC that we would not be able to comply with the KAYNN restriction due to the shortcut. The Controller directed the flight to 'Maintain the current rate of descent to cross KAYNN at 7;000 feet'; with the obvious implication that ATC didn't care about the speed but the altitude. The crew interjected that we were unable to exceed the maximum speed limits below 10;000 and below the LAX Class B airspace. The Controller soon switched the flight to another sector; with the discrepancies never being addressed. While the above issue regarding the published arrival was disconcerting; this Captain finds the apparent disregard of this Controller for FAR 91.117 absolutely alarming. This Controller clearly has no idea that the laws of physics are not negotiable; and that what he was asking this crew to do; in the time and space allotted; was simply not possible while remaining in compliance with basic FAR restrictions; and when the crew voiced their concerns; the Controller was unwilling to even acknowledge their concerns.The next time this Captain encounters these kind of ATC directions; he will be more directive and state in explicit terms: Unable to comply.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.