Regional Jet 700 ER/LR (CRJ700)
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Inflight Event / Encounter Other / Unknown
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Aircraft
I was the PIC of a CRJ700.  The aircraft was unable to reach its filed cruise altitude of 39;000 feet at a gross weight more than 1;000 LBS below the Bombardier charted maximum cruise thrust limited weight for the applicable ISA temperature deviation.  Upon reaching 38;300 feet at Mach 0.74; I stopped the climb at 300 feet per minute; leveled off; and instructed my First Officer to request FL370 from ATC.  We received the clearance to descend to FL370 and descended.  We remained there until we burned off sufficient fuel to place us at a weight 2;000 LBS below the Bombardier charted maximum cruise thrust limited weight for FL390 and the applicable ISA temperature deviation.  Once the aircraft weight was 2;000 LBS below the Bombardier charted maximum cruise thrust limited weight for FL390 and the applicable ISA temperature deviation; we again requested a climb to FL390; which were able to achieve at no less than a 500 foot/minute rate of climb.  This situation is not unique to this aircraft; as I have had difficulty climbing to high cruise altitudes prior to this.  I believe the entire CRJ-700 and CRJ-900 airplane fleet drag level may be higher than stated due to both: 1) Normal in-service deterioration; and 2) The CDL 57-41 telescopic anti-icing duct cover plate being removed from both wings; no performance penalty being assessed for the remaining hole in the leading edge of each wing;  and the subsequent associated increase in airplane total drag.  Accordingly; I believe the CDL may be in error for the telescopic anti-icing duct cover plate being removed from both wings.  I don't dispute that the takeoff and missed approach climb performance is negligibly impacted by these cover plates missing.  This is due to the slats being extended for takeoff and missed approach climb; and the drag associated with these openings having already been accounted for in the original certification basis of the aircraft.  However: 1) For the slats-retracted; one-engine inoperative final segment climb; 2) Enroute climb performance; and 3) One-engine inoperative; and all-engines operating altitude capability; I don't believe the drag increase is negligible.  For comparison purposes please review CDL 57-41 left or right wing slat seals missing.  Note that the drag associated with a wing slat seal missing causes a 660 LB/wing reduction to the enroute climb limit weight; increases the fuel burn by 1.55% per wing; and importantly; reduces the airplane's altitude capability by 500 feet per wing.  The wing slat seal is on the upper leading edge; and the surface area of the gap between the wing slats sealed by the slat seal is smaller in total area than the opening in the lower leading edge of the wing created by the removal of the telescopic anti-icing duct cover plate.  From an aerodynamic perspective; the impact of the removal of the telescopic anti-icing duct cover plate would appear to be greater than that of a missing slat seal; for three reasons: 1) The surface area is larger; 2) The wing surface behind the slat seal is smoothed for laminar flow with the slats extended; while the opening in the wing leading edge created by the removal of the telescopic anti-icing duct cover plate is directly ahead of the forward spar; creating spillage/interference drag in addition to bluff body parasitic drag; 3) The stagnation point of the airflow approaching the wing in a climb; and likely even in cruise is hitting  the opening in the wing; exacerbating the drag increase.  This is far from being a sole cause; however; if the above supposition is correct; then in some instances we are flight-planning aircraft to climb above their effective service ceiling; and setting up pilots for potential high altitude; low-speed excursions.  While there are acceleration factors involved; altitude capability or rate of climb at  its most basic level is: V x (T-D)/W; where: V = true airspeed; T = maximum climb thrust (CLB); D = aircraft drag level; and W = aircraft weight Given that our company weighs its airplanes every 36 months (or less; excluding short-term escalation for painting); and the aircraft weight and balance control program is predicated upon the statistically-sound methodology of AC 120-27E (as revised); I believe the aircraft weight is fairly close to the manifested weight.  Therefore I don't believe the airplane's weight is responsible for the altitude capability issue.  Next; given that our company uses a program for engine condition monitoring; it is likely that engines which are marginal in terms of their ability to produce 'rated' thrust are removed at; or prior to; their reaching their associated ITT limits.  Accordingly I don't believe lack of engine thrust is responsible for the altitude capability issue.  Using the process of elimination in conjunction with the argument addressing the airplane's drag level; above; I believe that the airplane's drag level is higher than stated; and is causing the aircraft to not attain its cruise altitude at the weight and ISA temperature deviation the aircraft manufacturer says it will.  Based on the following estimations I ran some drag calculations and estimate that the total drag (engineering normalized measure of airplane drag) increase for both telescopic duct anti-icing cover plates missing is roughly 190 LBS. Area of one telescopic duct anti-icing cover plate: 20 square inches; CD of the removal of one telescopic duct anti-icing cover plate: 0.80 Mach 0.76  The above suppositions and subsequent drag increase estimate may be completely out in 'left field;' but without exploring this with the aircraft manufacturer through both the Bombardier Technical Help Desk; and we won't know the airplane's true drag level and performance degradation associated with the removal of both telescopic anti-icing duct cover plates.
Reporter states that the worldwide fleet of CRJ aircraft have this CDL applied with no drag penalties.
CRJ-700 Captain reports his aircraft was unable to reach its filed cruise altitude of FL390 feet at a gross weight more than 1000 LBS below the Bombardier charted maximum cruise thrust limited weight for the applicable ISA temperature deviation.  He believes that all of his company's aircraft are equally deficient due primarily to  CDL 57-41; telescopic anti-icing duct cover plate being removed from both wings; with no performance penalty being assessed.