If it is daytime VFR it doesn't matter. At night it might be nice to have an accurate altimiter setting but with wing landing lights on it would be the same. Ask Sully if he ever looked at the altimeter and his reply would be WHY? Any competent pilot in visual conditions should be able to ditch by eye ball navigation. The altimiter is not required. This may not work for an autopilot monitoring pilot, only for a real pilot.